"Frontier in Space" is a high point from my favorite era of the show. While I adore the UNIT scenario, it is wonderful that the Third Doctors exile to Earth ended, freeing him to have adventures such as this. This story is far from perfect, but accentuates the strengths of the Time Lords third incarnation and casts some interesting light on this entire period in the shows history.
Doctor Who didnt attempt a sprawling space opera that often (only "The Dalek Master Plan" leaps to mind). There are many stories set in the future or on board space ships, but few serials present such an epic canvas which the characters are seen to cross: no "star map" of the Earth/Draconian Empires has ever been published by merchandisers, but none is needed: the script, dialogue, and production provide just enough for the viewer to visualize the rest of the landscape in the minds eye. Yes, there are several instances of obvious padding but even some of the repetitive escape/capture/escape/recapture sequences lend a feeling of a story happening on a vast scale.
Malcolm Hulkes script is quite good. There are occasional moments of embarrassing dialogue (The Doctor referring to Jo as a "perishing panda" and his anecdote concerning mind probes are best forgotten; as are, indeed, the very cliche of "mind probes"), but these are rare gaffes. Far better are the sequences on the lunar penal colony (The scenes between the Doctor and the other prisoners there are full of great character moments, and the Doctors exchange with Cross is very memorable. "Doctor: (after Cross confiscates another prisoners chocolate bar): Thats stealing, you know. Cross: Thats what Im in for ... Got a troublemaker, have we? Doctor: Thats what Im in for." In fact, watching this serial now, it is interesting to note how it anticipates the opening episodes of Terry Nations Blakes 7 in many ways.
The Draconians are a well-realized alien race: the scenes in their embassy on Earth and their home world suggest a well-thought out society, with plenty of room for further exploration. This, coupled with the excellent costume design, makes one wonder why they never featured in Doctor Who again. The Master is strangely comical in this outing: reading H.G. Wells and mocking everyone from the Doctor to the Daleks with equal scorn. Its well played by Roger Delgado but perhaps the Master could have been written in a slightly more sinister vein. This is a minor complaint, however, and Delgados swan song is very entertaining, nonetheless.
The Doctor is fascinating here; this incarnation is justifiably linked to UNIT in the minds of so many people, but it is always interesting to see him operating without the organization to fall back on. It is easy to forget that, whereas UNIT depends upon the Doctor, in the UNIT stories the Doctor himself also depends on UNIT for support and/or rescue. Without them, he and Jo are refreshingly on their own, depending upon their wits and whatever allies they can find to escape and win another day. Pertwees Doctor is not only the stylish moral crusader, but one of the most physically active incarnations of the character, engaging in hand-to-hand combat with Earth soldiers, Draconians, and the Master, undertaking several space walks to repair and or escape from assorted space vessels, and so on throughout the tale. Storylines are obviously tailored for whatever Doctor is incumbent at the time, but it is interesting to ponder how well Doctors would have fare if placed in some of their counterparts serials.
As for Jo Grant... Hmmm. I am partial to Liz Shaw, myself, but Jo doesnt come off too badly in this story. She resists the Masters hypnotic effects and diverts attention from one of the Doctors escape plans (for a while, at least), proving herself far more capable than I have considered her in the past. In Episode One, she even deduces that the Daleks might be in command of the Ogrons, only to be shot down by the Doctors contention that Ogrons have many employers. All right, the Master was guiding the Ogrons, but the Daleks were ultimately involved as well! Perhaps its time for me to re-evaluate Jo Grant?
Perhaps the only disappointing feature for me is the final sequence. It provides the cliffhanger lead-in to "Planet of the Daleks" well enough, but, in a piece of poor (one might even say bizarre) editing, the Master simply disappears! He shoots the Doctor one moment, and then the Ogrons flee, leaving Jo to help the wounded Doctor into the TARDIS. In an eyeblink, the Master is nowhere to be seen! Where did he go, and why? This always puzzled me, and, coming right at the end of the story, it closes out the tale on a slightly unsatisfactory note. Nevertheless, director Paul Bernard does a fine job otherwise, and "Frontier In Space" remains, for me, one of the greatest successes of the Pertwee era.