'Frontier in Space' marks the final appearance of the Roger Delgado Master, due to Delgado's tragic death shortly afterwards. Despite some padding, it is on the whole a fine swansong for Delgado, who puts in one of his finest performances.
The Doctor/Master rivalry reaches its peak here, as for once, the Master comes close to winning. This is reflected in his attitude towards the Doctor from the moment he first appears in Episode Three. As I've noted previously, during his first four stories, the Master was often quick to find excuses not to kill the Doctor, seeming to want his approval. This changed at the end of 'Colony in Space', when the Doctor refused his offer of a half share in the Universe, after which all his attempts to kill the Doctor seemed genuine. Having been repeatedly defeated, we may assume that the Master had finally had enough of being thwarted and decided to stop playing games. Here, the emphasis shifts, as the Master retains the upper hand until the very end of the story. By the time that the Doctor materialises on board the Earth cargo ship in Episode One, the Master has already sown the seeds of war and remains convinced until Episode Six that the Doctor is too late to avert it. He's almost right, as witnessed by the fact that until the Doctor reaches Draconia, nobody except the imprisoned Professor Dale believes his story about Ogrons. As a result, the Master can afford to enjoy his victory, which is precisely what he does. When the Ogrons bring him the Doctor's TARDIS, he immediately sets out to recover both Jo and the Doctor, and on meeting them both he is at his most charming. Indeed, he's almost jovial. This continues until the very end of the story; even when his ship is captured by the Draconians, he remains relaxed because he knows that the Ogrons are on their way to rescue him. He loses his temper briefly when the Ogrons leave one of their number behind, which is just the proof that the Doctor needs to avert the war that he has been fermenting, but on recovering the Ogron - and taking Jo hostage - he soon regains his composure. Even when the Doctor discovers his base he is smug, clearly relishing the idea of springing his allies on the Doctor. It is only at the very end of the story, when General Williams and the Draconian Prince escape and the Doctor reaches his TARDIS that he realises too late that he should have killed the Doctor earlier. Unfortunately, the ending of Episode Six of 'Frontier in Space' is horribly edited, so that this effect is rather lost; the Master loses off a shot at the Doctor and wounds him, but then vanishes. This suggests, rather implausibly, that the Master's own hypnotic device has affected him, resulting in a rather unsatisfactory final scene for Delgado. Nevertheless, overall the finale of the Third Doctor/Master conflict works well, allowing the Master to regain some credibility.
In contrast to the Master, the Doctor has a rather undignified time during 'Frontier in Space', spending most of it either locked up or under interrogation. This is obviously padding, but it is an example of padding that works, thanks to a combination of a good script and excellent performances from Pertwee and Manning. Pertwee still seems to be enjoying himself again, making the most out of the dialogue between the Doctor and Jo, so that their often lengthy conversations whilst locked up work to demonstrate the genuine warmth between the pair of them. In addition, since this is the last appearance of Delgado in the series I found myself thinking back to 'Terror of the Autons', which reminded how far Jo has come. From the easily hypnotized, almost vacuous character she appeared to be in her debut, she has developed into a resourceful companion who now stands up to the Master defiantly (her steadfast refusal to be hypnotized by him in this story is marvellous) and takes being locked up and threatened by Ogrons in her stride. Manning's delivery of the dialogue she's asked to spout whilst the Doctor is making his furtive space walk outside the Master's ship in Episode Four is cringe-worthy, but I assume that this is intentional, since the Master looks bored with it and turns the sound off. Despite being a frequent prisoner here, the Doctor still gets some great moments, particularly when he wins over the Draconian Emperor. Thus, in a story that asks little of them in terms of action, both of the main characters still manage to shine.
Characterisation being Hulke's forte, there is plenty on display here. Even minor characters are rendered three dimensional via throwaway lines, so for example the officer who arrests the Doctor and Jo on board the cargo vessel at the start of episode two is present when they are taken to their cell, and promises to arrange some food for them. This is irrelevant to the larger story, but shows this minor character to be more than just a uniform. Similarly, the two members of the cargo ship's crew react differently when they are first threatened by the Ogron ship, the Captain insisting that they make a stand and defend their cargo, whilst his terrified companion begs him to surrender. The script is full of these minor details, which add touches of character to the supporting cast. The two main groups of characters other than the Doctor and Jo and the Master and his Ogrons are of course the Draconian and the human governments. In the case of the humans, we only really see two people of significance, General Williams and the President. Hulke skillfully includes in his script hints of a larger government, with talk of a senate and suggestions that an ineffective President can be removed from office. This avoids the problem of trying to suggest that a President of the entire planet would rule virtually single-handedly, whilst simultaneously allowing for a small cast. Here again also, the characterisation of these characters works well, especially in the case of General Williams. On two occasions, expectations are subverted, first when the General, obviously frustrated with the President, nevertheless makes it clear that he will not betray her, and alter when this supposedly xenophobic warmonger realises that the war he caused previously between Earth and Draconia was the result of a terrible misunderstanding on his part. Impressively, he quickly admits his mistake and apologizes, looking suitably repentant. Admittedly, neither Michael Hawkins nor Vera Fusak put in especially captivating performances, but the scripting shines through nonetheless.
In the Draconian court, the effect is much the same, with talks of the Emperor depending on the great families for support, and the Emperor (played by the ever-reliable John Woodnutt) palpably older and wiser than his hotheaded but ultimately noble son. Again therefore, Hulke hints at a wider society. Indeed, the Draconian custom that women may not speak in the presence of the Emperor gives us further insight into their society, as does the importance that they place on honour, both providing glimpses of a wider culture. The prisoners on the moon whom the Doctor encounters are also well characterised, from the (rather strange) Peace Party lynchpin Professor Dale, to the idealistic Patel, to the untrustworthy trustee Cross. Even the briefly seen Governor is well characterised, a petty, rather cruel, man basking in the power he holds over his prisoners and inflated with self-importance.
The return of Ogrons is of little importance, given their role as stupid henchmen, but since they served the same role in 'Day of the Daleks', there's no real reason why they might as well not be used. More important is the fact that anyone familiar with their previous appearance might put two and two together and realize who the Master's mysterious employers are. Even with foreknowledge however, the appearance of the Daleks in Episode Six is a great moment, as they glide into view on the cliff-tops and casually gun down the Earth soldiers. Once it becomes clear that the Daleks are behind the attempt to start a war between Earth and Draconia, it immediately offers the potential of an epic story to come, suggesting perhaps that the Daleks on embarking on some campaign on the scale of that in 'The Daleks' Master Plan' or 'The Evil of the Daleks'. The cliffhanger ending to 'Frontier in Space', as the Doctor sets off in pursuit of the Daleks, therefore has tremendous promise. Unfortunately, what it delivers is one of the worst stories of the Pertwee era...