Not exactly painfully mediocre - but not exactly great either.
This pretty well sums up "Planet of Evil" in my book. It's a solid little Tom Baker tale with an interesting monster, a bit of an overused premise and a lot of fun on a spaceship and jungle set! It serves up a nice adventure but it really doesn't stand out much in anyway. Which, when you think about it, is the case with quite a bit of the Tom Baker era. Yes, he has some of the best stories the series ever saw, but when it's not one of those classic stories, we get some pretty "paint-by-numbers" storytelling going on. Though "Planet Of Evil" exemplifies this idea quite heavilly, I'd still say it's a bit better than a lot of the other more bland Who stories of this era.
The jungle set is, of course, one of the most memorable aspects of this story. I won't go on about it too much because lots of you already have. But it certainly looks gorgeous and shooting it on film makes it look even better. By contrast, the spaceship interior looks like it was cobbled together by multiple other spaceship interiors used over the years on the show. There definitely seems a lot of "Ark In Space" and "The Mutants" stuff in there. Which just gives the story even more of a "been there done that" kind-of-feel. Not only are certain elements of the script re-hashed - but so are certain elements of the set!
Which is the biggest problem this story suffers. The "scientist meddling with powers he shouldn't be meddling with" concept has been so overdone by this point in the show's history that it seems almost laughable that the Doctor is being so dramatic about it all. You'd think he'd be so tired of arguing with stupid scientists by this point that he would just club them over the head - stop whatever project it is they're working on - and head back to the TARDIS by the end of episode two! But, instead, we get the usual runaround where the Doctor pleads endlessly with Sorensen to abandon his research whilst dealing with various plot complications created by other members of the supporting cast. It's all pretty "pantomime", really. Even though the Doctor's quote about a "scientist's ultimate responsibility" is very well-delivered.
By the same token, there are some elements to this story that make it a bit "fresh" too. The use of the TARDIS in this story was quite unusual for this era. Usually, the TARDIS serves as merely a way to get the main characters to the story location. The fact that it's instrumental in saving the day is a bit unusual. Which is a nice touch.
I also enjoyed the way the millitairy team is presented. The concept of a Captain and a Senior Officer is sort of a neat one which kind of makes sense in some ways but would also be a breeding ground for power struggles (which is, inevitably, what happens by episode four!). I also quite liked the burly crewmember whose name presently eludes me. A nice little bit of comic relief in a tale that tried desperately to take itself seriously all the time (even though, as always, we get some pretty laughable-looking effects that become even more laughable because it's all trying to be so dramatically intense).
A third nice strongpoint to this tale is the way we see that the Doctor is "not without influence" because of his status as a Time Lord. It's a neat sort of concept that lends a deeper image of power to his origins. Anyone else falling into that pit just plain dies. But the Doctor, because of who he is, is able to communicate with the anti-matter monster and reach a resolution to the plot. And the actual sequences in the void are very surreal and well-achieved. Another point many of you have made so I won't go into it more than I have to.
Now, we come to the performances of the supporting cast. We have, quite noticeably, the notorious Prentis Hancock back on the scene. Sorry to sound so catty, but who the hell told this guy he could act?! So wooden and yet trying so desperately to be dramatic. It all looks quite dreadful. In harsh contrast, the casting of Sorenson was a great move. He is played to perfection, giving us all the right emotions at all the right times. Watching the actual scenes where Salamar and Sorenson are playing off of each other are almost like having a plate of filet mignon and human fecal matter placed in front of you and being told to eat it!
Ew. That was a gross mental image.
Anyway, moving on to some other performers. I loved Tom Baker's work in this story. This is all way before he went so zany with the part and I really enjoyed just how serious he could be sometimes. Particularly in this story. It's almost as if the removal of the scarf in episode two is symbolic. He recognises that it is a bit of a silly piece of costuming and ditches it so he can get really dramatic for the final two episodes.
And now, another harsh contrast. One that I'm sure a lot of you will take great issue with. I'm sorry folks, but I was never quite sure what was the big fuss about Lis Sladen. Her character with Pertwee, though a bit "choppy" in places, was far more interesting. By the time we get to second season Tom Baker (as we are in this story) she has become such a blatant plot cypher that I really find her to be practically characterless. She's still not quite as dumb as Jo Grant, but boy can she stumble around, get into trouble and then get rescued! Or, on a rare occassion or two, she can actually be able useful and help the Doctor. In Planet of Evil, she displays this mediocrity of character in great abundance. I don't blame the actress too much - moreso the poor scipt-writing. This is frequently the case with the Doctor Who when the protagonist is travelling with just a single female character from the twentieth century. She's used to serve the plot rather than given a lot of interesting nuances to her personality. Only with latter-day examples like Ace and Rose has this problem been solved. Whereas poor old Sarah Jane, to me, seems about as cut-and-paste as the female companion can be in this story.
Wow, it was tough writing that last paragraph knowing how much some of you will be offended by my heresy. But now, let's move on:
My only other big bone of contention with this story is that it really does lose steam in episode three. The tribute to Jeckell and Hyde, though nice in some ways, is blatant padding. A desperate attempt on the writer's behalf to introduce a subplot virtually out of nowhere that will fill the episode and get us to part four. It's a pity the show was so dedicated to evenly-numbered stories during this era. Part three could have easilly been chopped out and we could have been given a nice tight three-parter that might have moved up the callibre of this story quite significantly. Just think of how enjoyable stories like "Happiness Patrol", "Survival" and "Ghost Light" were in the late 80s because they didn't force themselves' to just "put in time" til they got to that fourth episode. Sadly, no such luck here. Instead, the story gets slowed to a bit of a snail's pace until it can be brought back up to steam for a nice climax in the final episode.
Still, overall, I'd rather put this story more in a positive light than a negative one. There are a lot of strongpoints here with a few negative aspects that drag it down a bit. It's a good solid story with a nice sense of adventure to it. Very dramatic and intense and much of that drama is used very effectively. Better than most of the "blandness" some of the Tom Baker era suffered.