With the sixth episode we are plunged back into Martha's world. A world of DNA experiments and mysterious men in black. Stephen Greenhorn takes the standard comic book cliches, invoking 'Spiderman' and 'The Hulk', pays homage to the venerable Nigel Kneale's 'Quatermass' and SF B movies such as 'The Fly' and then plugs it into the main themes now beginning to run through the series - what does it mean to be a human, is there hope in a callous age and can those blessed with the gift of immortality have real faith?

Richard Clark again shows how good he is with visual composition here with lots of tracking and overhead shots, a particularly stunning revolving shot (an homage to the 'Alien' films) as the CGI monster climbs the ceiling of the corridor, and some lovely bits and pieces glimpsing characters through arches and doorways in the cathedral. He gets a great deal out of the laboratory setting too, using reflections and back-lighting to great atmospheric effect. Another very handsome looking episode.

Book-ending the episode are two scenes between the Doctor and Martha, one where the Doctor simply feels it is time to let go and one where he finally understands that Martha doesn't wish to be left behind. In between these two points, we have a narrative in which Martha plays a significant role - being resourceful, using her skills and finally going back into the conflict to face the consequences and ultimately to the cathedral where she offers herself as bait to lure Lazarus to his destiny. I don't think the relationship between the Doctor and Martha is a carbon copy of the one he had with Rose. This is more about being an equal, facing the odds with intelligence but perhaps with a pinch of unresolved sexual tension. More Martha Peel to Doctor Steed, I think.

Below the monster runaround there's also a great deal more going on.

Lazarus and his laboratory represent the scientific principle when it comes to extending life. To him it is a matter of DNA manipulation, patenting the idea and raking in the cash. The DNA manipulation machine is more or less Lazarus' electronic God. Aptly, when Lazarus takes his spin in the machine, he isn't resurrected and given new life but merely reduced to the function of the Grim Reaper itself, bringing death and destruction to himself, his wife and others. Rather than enhancing life, he subtracts and extinguishes it.

However, as Lazarus may see death as the end of the lane as far as the journey of life is concerned, the Doctor understands why the human span must end. Death to him is seen as a valuable experience for human-kind, one that he himself seems to crave here. He sees death as not just something the body must face but also as something the entire being must embrace. It's something he has been denied and where prolonged life is a curse jn which mortals he has dearly known wither and die. Immortality is regret, sorrow and loneliness.

Lazarus' transformation is an opening of Pandora's box in a literal sense when he uses the machine. 'Tonight, Matthew, I'm going to be Orpheus in the Underworld' - cue dry ice and a personification of the circle of existence, the self-devouring worm muching up mankind.

The final showdown in Southwark cathedral, superbly played between Gatiss and Tennant, reverses the cold, analysis of the flesh as seen in Lazlabs for the echoing magnificence of faith's cradle. Where the lab maybe Alpha, the cathedral is Omega - a physical playing out of life's paradoxes, of beginning and ending - and the cathedral with its stained glass, vaulted roof and resonating sound is where Lazarus has a chance to empty himself of his ego, abandon hubris and rely on faith and hope to see him through to the end of his days. It's continuing a religious theme, centred on the transformation of mortal beings through ascension and faith, first intimated in 'Gridlock'.

So, kudos to The Mill once again for their CGI monster. Not bad at all, particularly in the scene where it's scuttling along the cathedral roof. This and Gatiss' very physical performance helped us to imagine the transformation scenes without actually having to spend lots of money showing them. The make up for Gatiss was exemplary and he found ways to work with it to create the character fully and to the extent that in the end we understood Lazarus' folly and sympathised with his failed desire in the sad coda of the death scene.

It was a good, slightly old fashioned monster romp, with even a 'reverse the polarity' nod thrown in to underline the Pertwee vibe, and it often veered into camp with Gatiss (very Julian Glover like) and Thelma Barlow deliciously crossing swords. Martha's family were fleshed out effectively and her mother Francine, played with seething suspicion by Adjoa Andoh, provided a pleasant flash back to the infamous Jackie Tyler slap and offered a tantalising glimpse of future betrayal perhaps. Tish Jones was effortlessly provided by Gugu Mbatha-Raw and I'd like to see more of Leo Jones played by the lovely Reggie Yates. They all provided the necessary grounding for the Martha character, an indication of future loyalties, without ending up being a re-hash of the Tyler clan.

Tennant and Agyeman were excellent, the interplay in Martha's flat a specific treat, knickers and all! And finally, Martha is welcomed as a fully paid-up crew member after a string of episodes that have drip-fed us the unresolved nature of their partnership. With more mentions of Saxon (Harold) here and an extended trailer for the second half of the series, I get the impression that events are going to move up a gear now.

Despite the slight apathy I was feeling after last week's episode I had regained my Doctor Who excitement by mid-week, no doubt at least partly thanks to a shiny new issue of Doctor Who Magazine and a few sly episodes of Frontier in Space. Therefore all was right with the world again when I sat down to watch episode six of the third series; The Lazarus Experiment.

Fairly straight forward story but so well executed. The Doctor gets to be a proper science whiz and fiddle with wires and all that sort of boffin stuff, Gatiss was excellent as a baddie not so far from the Doctor's level of intelligence and I loved their scenes together. This episode makes Mark Gatiss only the third person to have written for and acted in Doctor Who since 1963. I bet he's pleased as punch (whatever that does mean). He must have been thrilled to be a part of an episode that homage's Nigel Kneale as much as this one does with all its science tapping into ancient horrors. Thelma Barlow was an unexpected boon in this story as I hadn't expected a great deal from her part. Lady Thaw was as much of a monster as Lazarus.

The monster was grotesque and well realised. Scrabbling along corridors and leaping across balconies. Very scary.

Mr Saxon's Evil Little Helper was a nice touch - really building him up aren't they. How long has he been watching the Doctor? Since Canary Wharf? Since the Sycorax invasion? Since the Slitheen? He must be very well prepared to take the Doctor on when he's good and ready. Whoever he is.

Not crazy about Martha's family but they serve their purpose. Considering her Mother seems to have an extra function as Mr Saxon's pawn I'm not thrilled with the acting so far; Adjoa Andoh seems to be a bit more Albert Square than the Powell Estate. Also it seems to me that Reggie off of radio one may as well not be in it so far. Why were they all invited to this experiment anyway?

Martha is brilliant and I much prefer her to Rose; and also that her relationship to the Doctor is very different. The Doctor manages to be rude or insulting to her at least once an episode - which I love. He's got a real edge to him now. She keeps making moon eyes at him though so I guess that'll be where it goes.

DT, free of the winking atavism of last weeks closing scenes, is splendid here. Cool and distant to Martha at the beginning; his interaction with Martha, her Mother, and most of all Lazarus is a pitch perfect pleasure. Best of all is the Cathedral conversation between Lazarus and the Doctor. 'You think history's only made with equations?' Lot's of great dialogue throughout the script.

With it's glossy look and fast pacing topped off with multiple climaxes, this story felt more like a good old fashioned SF blockbuster and I think that was the right thing to follow last weeks psuedophilosphical clunking imagery and Star Trek sentimentality. As a result I was already grinning all over my face when the episode ended...

AND THEN... there's the trailer. We're halfway through the series and at the risk of jinxing it I don't see what can go wrong with any of the remaining episodes, Jack, Saxon, Cornell, Moffatt, Chibnall, Derek frickin' Jacobi! If the scarecrows and spaceships and explosions weren't enough for you there's John Simm in a room full of dead or incapacitated people wearing a respirator and tapping the table. The scariest thing I've seen in Who yet.

Vote Saxon!

Something different for Doctor Who, a "realtime" epsiode. My dad asked what that meant when he read it in his TV guide. So we knew we were in for something of a rollercoaster ride.

The Doctor and Martha answer a distress call and find themselves aboard a space ship which is crippled and headed for collision with a sun. Later it becomes clear that the sun, or something in its corona is alive and in illegally scooping up the star's energy for their engines the crew have sucked up the "heart" of the entity into thier ship....and understandably the creature is not overly happy about this!

One of the crew is taken over by the entity, whcih proceeds to take its revenge by picking off the crew one by one. Wearing a rather creepy face mask, every time it lifts the visor it shines what looks like sunlight onto its victim who is incinerated.

The Doctor and Martha of course have 42 minutes to save the day, which they do by finally realising what has happened and dumping the contents of the fuel chambers back into the area they scooped it from.

I liked the concept of a different kind of entity/lifeform. Its not entirely original but its unusual, a better idea perhaps than the Isolus from last year's "Fear Her".

Martha as a character came into her own when she was separated from the Doctor and trapped into an escape pod with a crew member. In that scene she earned her stripes as a top class character, companion and Freema is undisputably an excellent actress. The pod slowly, agonisingly moves away...and Martha bangs on the window asking for help, while the Doctor says "I'll save you" but of course neither can hear the other.

The tention is built up skillfully, something to do I think with Graeme Harper's direction and Chris Chibnal's script. At times this had a similar feel to "The Satan Pit", perhaps because of the claustrophobic space ship setting. The resolution was satisfactory, and we were finally treated to the poignant moment where the Doctor gives Martha the TARDIS key as a "frequent flier" bonus.

Then, the final scene...where Mrs Jones is clearly helping Mr Saxon track down the Doctor. Of course she believes Saxon is doing good, and is worried about her daughter. That was all done well. the Saxon references and the Jones family are being handled better than Torchwood and the Tylers generally were in 2005/6.

Overall I enjoyed, but it seems this series is stuck in fourth gear and unable to go up into top. Rather fourth than second, however.

8/10

When you mix together a lot of ingredients, you are going to get a dark brew, and this is what The Lazarus Experiment turned out to be. I am not sure if I know the exact recipe, but I think that first you add a healthy dose of Robert Louis Stevenson's Doctor Jekyll and Mr. Hyde, together with a dash of David Cronenberg's The Fly. Then you give the whole thing a classic biblical setting straight from the eleventh chapter of St. John's Gospel, and you throw in some obtuse quotes from T.S. Eliot's The Waste Land and The Hollow Men. You sprinkle the whole thing with some nifty CGI, some effective makeup and promising new characters just waiting to be developed in future episodes, and you have got a very entertaining episode six.

Doctor Lazarus is a mad scientist in search of the fountain of youth. Unfortunately for him, it does not come as easy as it does in Oscar Wilde's great novel, The Picture of Dorian Gray. In that great decadent Victorian work, Gray does not actively seek youth by scientific means, it just comes to him one day via art and the kind of artifice that verges on magic. In The Lazarus Experiment, the title villain works towards similar results by using the time-tested traditions of sci-fi mad scientist research. For both Gray and especially for Lazarus, eternal youth carries some dire results, plenty of drawbacks, and the kind of side-effects that should make any rational thinking man of science throw out his bunsen burner and dedicate himself to less dangerous work. Lucky for us and humanity, the Doctor happens to be in attendance at the unveiling of Doctor Lazarus's creepy way-back machine, and he is able to thwart the horrible side-effect mutation that creeps into Dr. Lazarus's existence in the very same way in which Mr. Hyde often usurped the body of his literary better half.

The entire episode, like Wilde's literature, has an inescapable end of the century moldy air to it. It starts with the great old man makeup that transforms actor/writer Mark Gatiss (he is the author of one of my favorite Dr. Who episodes: The Unquiet Dead) into a seventy-six year old ready to be reborn. Throughout the episode we feel that we are nearing the end of something, but we are not quite sure what it is. The TARDIS's return to Martha Jones's apartment, at the start of the episode, for instance, is described as "the end of the line," and the show's denouement concludes at dark, empty, centuries-old Suffolk Cathedral with a monstrous Dr. Lazarus falling from the bell-tower ? the fall of Lucifer ? to the strains of a pipe organ, with all the stops pulled out that turns out to be the not too convincing deus ex machina of the story. By the way, this quasi-musical tour-de-force banging on the organ's keys and pedals is played by the Doctor with the kind of aplomb that would make the Phantom of the Opera really envious.

This episode delves further inside the relationship between Doctor and new companion, by exploring Martha Jones's family. We are introduced to her sister, who works for Dr. Lazarus, and we also get to meet Martha's brother and her mother. Mrs. Jones, portrayed by Adjoa Andoh, is one tough lady who, right from the start of the episode, seems to have made up her mind that the Doctor is just no good for her baby. In addition, a mysterious man named Harold Saxon, whom Mrs. Jones meets at Lazarus Laboratories, manages to completely poison her mind against the Doctor by revealing to her a secret that culminates in Mrs. Jones attacking the Doctor's face with an old-fashioned slap. The Doctor's precious comment about mothers as he rubs his sore cheek was the comedy highlight of this dark show.

The Lazarus Experiment turned out to be a heady, neo-baroque concoction that will surely set the stage for the upcoming episodes that will follow. By the looks of it, the episode that will air in two weeks promises to be one of the most memorable of this remarkable season.

After the unwieldy and ultimately disappointing 'Daleks in Manhattan'/'Evolution of the Daleks' comes 'The Lazarus Experiment', an episode that is pure filler, with a clich? ridden plot that sees a mad scientist accidentally turning himself into a monster that devours people, and eventually falls to its death from a bell-tower, but hugely entertaining nonetheless.

Professor Lazarus is like one of those old Marvel super-villains whose name predicts his fate, but rather than going for a simple Jekyll and Hyde scenario, writer Stephen Greenhorn creates an arrogant, cruel and deeply unpleasant character, a fact that starts to become obvious before his transformation when he clumsily gropes Tish's hand. Following his rejuvenation he becomes a proper gloating villain, showing no remorse for the fact that he now has to suck the life-force from other people to survive, and who coldly rejects Lady Thaw, revolted at her decrepit form now that he is a young man again. It all makes for very traditional villainy, and Mark Gatiss is perfectly cast in the role, hamming it up with glee and managing to be enormously entertaining in the process. In contrast to, say, Roger Lloyd-Pack's brand of "Bwa-ha-ha" ham in 'Rise of the Cybermen'/'The Age of Steel', Gatiss reigns in the over-the-top aspects of his performance just enough to make Lazarus rather fun, and clearly throws himself into the part with enormous enthusiasm, which rubs off on this viewer at least. He's also especially good when Lazarus is reflecting on the past, particularly when he's drenched in sweat and wrapped in a blanket in the cathedral.

Greenhorn also uses Lazarus to make comments about the nature of humanity, but does so in slightly less obvious ways than I first expected when I first heard the line "change what it means to be human", and in doing so makes him a suitable match for the Doctor. Simply put, when the Doctor is pompously telling Lazarus what humanity is all about, Lazarus' rejoinder that the desperate need to survive is very human is quite true, and tellingly when he scathingly asks the Doctor "who are you to judge me?" the Doctor doesn't seem to have a convincing answer to hand. The Doctor's initial objection to Lazarus' experiment prior to any obvious drawbacks also briefly makes him look like he arrogantly opposes any scientific development that he doesn't like, and this works well in context, as a mysterious suited figure whispers dire warnings about him into Francine's ear, a fact which the Doctor remains oblivious to here. The end result is that the Doctor's bull-in-a-China-shop approach to meddling without bothering to explain anything to anyone starts to make him look rather questionable to anyone who doesn't know him, and coupled with more references to the mysterious Harold Saxon, who obviously knows who the Doctor is, starts to give the impression that he's being slowly outmanoeuvred.

Tennant continues to be more restrained than in the past, and his frantic game of cat-and-mouse with Lazarus is very entertaining, as he improvises on the fly, blowing up laboratories, and desperately locking doors behind him in a bid to slow Lazarus down. More technobabble is used to get him out of trouble, but when he's forced to improvise inside Lazarus' machine and temporarily deals with his enemy by reversing the polarity of the machine, Greenhorn's insertion of the line "really shouldn't take that long just to reverse the polarity, must be a bit out of practice" makes it feel like a pleasing nod to the past. I also, in principle, like the idea of the Doctor despatching the monster with manic organ playing, although points are deducted for using the Davis ex machina as window dressing, as well as using it as a DNA detector earlier.

Martha's intelligence seems to have diminished somewhat since 'Smith and Jones', as she becomes a generic companion here, but she is quick-witted enough to realised that she has collected a DNA sample from Lazarus, and she also gets to show bravery whilst distracting the monster at the end. The Doctor's casual dumping of her back home also works well, since when he offers her a longer-term trip on board the TARDIS at the end, he looks a bit like a disappointed child when he thinks she's refused: this harkens back to the "my best friend" attitude of the past, and for all of Martha's obvious attraction to him, I find I can cope with the companion fancying the Doctor as long as it isn't reciprocated. In fact I endured it for two years with Sam Jones, and it was by far her least irritating attribute. We also get reintroduced to her family for the first time since 'Smith and Jones', and as I suspected at the time they are vastly less irritating than Rose's were. Most importantly, they also seem to be serving an actually purpose, with Francine's concern for her daughter entirely reasonable and believable, as she is warned that the Doctor leaves death and destruction in his wake. Greenhorn keeps the soap opera to a minimum, with even the sibling rivalry between Martha and her sister seeming like convincing background detail rather than something to be dwelt on.

The CGI monster frequently just looks like a CGI monster, and I can't help wondering if this series flaws derive from the self-congratulatory back-slapping of the production team, with nobody willing to acknowledge the programme's short comings, but for the most-part 'The Lazarus Experiment' is nothing groundbreaking, but is a very entertaining romp. And once in a while, there's nothing wrong with that at all.

Almost halfway through Series 3 and, after two trips to Earth's past and one to New Earth in the distant future, we're back to present-day London. These episodes haven't tended to be amongst my favourites since the series returned - no particular objection to them, I just have a personal preference for "historicals" and "other planets", as I think they're more interesting settings.

And this one, although eminently watchable, didn't change my perception about present-day London as a setting. Again, I must harp on about the episode length - there really isn't that much you can do plot-wise in 45 minutes (and the running time of this was very short, a lot closer to 35 minutes) and, as a result, the story is over before it's begun.

So what was this latest short story all about?

The Doctor takes Martha back to Earth after her "one trip" in the TARDIS but, just as he's about to leave, his interest is piqued by a TV news item featuring Martha's sister, Tish, a PA, and her boss, the ageing Professor Lazarus.

At a demonstration in Lazarus Laboratories, The Doctor, along with Martha and Tish and their mother and brother, watch in amazement as Lazarus performs an experiment using his Genetic Manipulator, from which he emerges 40 years younger. He believes this discovery of cheating the ageing process is set to transform the human race.

The Doctor works out that Lazarus has altered his DNA to change his molecular structure, but a side effect is that he transforms into a monster which drains the life force of humans. The Doctor manages to lure the creature away, so that the guests at the demonstration can flee and, once she is sure her family are OK, Martha returns into the building to help her new friend.

They think they have destroyed the creature, and it reverts to the form of Lazarus. However, the ambulance which takes the body away suddenly stops, and The Doctor realises Lazarus has indeed risen from the dead. Pursued by The Doctor, Martha and Tish, Lazarus heads for a nearby cathedral.

Meanwhile, a "mysterious man" takes Martha's mother to one side, and warns her about The Doctor.

In the cathedral, Lazarus once again reverts to monster form, and chases Martha and Tish to the bell tower at the top. Just in time, The Doctor kills the creature for good by playing the organ which creates massive sound waves that revorborate off the bell.

The Doctor agrees to Martha's request for more than "one trip", and she joins him full time in the TARDIS. As it dematerialises, Martha's mother leaves an urgent message on her phone, warning her to leave The Doctor because she's in terrible danger . . .

The story itself - mad scientist's quest for eternal youth/immortality/turns into monster/dies wouldn't win any prizes for originality, but it was a perfectly-decent romp - although, even for Doctor Who, they might have been over-quota for running!

Writer Stephen Greenhorn's debut episode for Doctor Who had plenty of good dialogue for the main characters, though, and the script was well served yet again by David Tennant and Freema Agyeman as The Doctor and Martha. Some humorous moments, too - The Doctor grabbing Martha's underwear from a clothes horse in her flat to her horror, Mrs Jones dealing a hefty slap to The Doctor (shades of Jackie Tyler to the previous incarnation), and the monster itself (peek-a-boo) being given a character.

Mark Gatiss was also excellent as the older and younger Lazarus, particularly the former, which he seemed to relish. I was actually more taken with the prosthetic work to make him up into the 76-year-old Lazarus than the CGI monster, impressive beast though it was. And Gatiss, as a DW fan and dual writer for the series, knew how to pitch the villain so as not to make him over the top. Good performance, and some nice scenes in the cathedral with his friend, Tennant.

It was always going to be a big ask to integrate three members of Martha's family, and Reggie Yates as Leo was the big sufferer of time constraints here, unless there's an award for "standing there". More substance to Gugu Mbatha Raw as Tish and Adjoa Andoh as concerned mum Francine, and it'll be interesting to see them again, as we undoubtedly will later in the series.

Plenty of "green screen" acting and, again, kudos for Tennant, now an old hand at acting against nothing. I'm finding it difficult to find any fault with the show's star at the moment.

No denying that The Mill's latest CGI masterpiece did what it said on the tin, and filled the screen magnificently, but these creatures are rather one-dimensional in that after devouring a couple of sacrificial extras, all they can really do is chase people down corridors. We've seen it with the Reapers, The Werewolf and the Krillitanes - plus the static CGI creatures in Rose, The Long Game and The Satan Pit - all very different visually, but limited in what they can actually do. And, speaking of limits, there is a finite amount of times you can go to a well. I think we might be close to the bottom of this one.

Intriguing titbits for future episodes, with more mentions of Mr Saxon, who was the paymaster behind Lazarus's experiment. We now know Saxon's first name is Harold and has, through an intermediate (who rather reminded me of Willy Wonka's sidekick who tried to bribe the golden ticket winners in the original version of that film), started to sow seeds of doubt about The Doctor with Martha's mother. And just a little hint that there may be a touch of sibling rivalry between Martha and Tish, which may also prove significant.

Good, too, that Martha (probably the most-eager-ever incumbant of the companion role - even more than Rose) has convinced The Doctor that she is worthy of a regular spot in the TARDIS. There are similarities with Rose in that she has already effectively suggested she would choose The Doctor over her family, but there is no indication in the slightest that The Doctor sees her in any other terms than a companion. She has been an excellent addition to the show - both character and actress - since her first scene really. Particularly pleasing that, like Rose, she takes an active part in the solving of the mysteries and using her own initiative, rather than just being The Doctor's foil. Makes her a much more rounded character.

On the whole, more filler than thriller, but pretty slick, and hard to criticise. But no more than 7 out of 10 because most of it has been seen in various guises before. However, I do believe there is better to come, and we haven't seen anything like the best of this series so far.