Written by: Malcolm Hulke
Directed by: Paul Beranrd
Materializing aboard an Earth spaceship in the year 2540, the Doctor and Jo are only beginning to explore when the ship is attacked. The ships' crew are clearly under some sort of influence, as when they look at Jo and the Doctor, they see them as Draconians, an alien race whose empire is currently in heightened tensions with Earth following a war. The attackers board the ship, and the Doctor and Jo discover that they are Ogrons, brutish thugs for hire they've encountered before. However, like their perception of the Doctor and Jo, the human crew see them as Draconians.
The Ogrons steal the ship's cargo, including the TARDIS, and leave. The ship is rescued by another Earth ship, and the authorities on board imprison Jo and the Doctor for transport back to Earth under suspicion of spying for the Draconians. Though the Doctor tries to convince Earth's president and her advisor General Williams that the situation is being manipulated to push Earth and Draconia into war, his pleas are not believed, and he is sentenced to imprisonment on the Lunar Penal Colony.
Meanwhile, Jo is held prisoner on Earth, and false records soon are discovered that claim both she and the Doctor are career criminals wanted on Sirius 4. A Commissioner from that dominion is arriving to take her into custody, and to Jo's shock that Commissioner is revealed to be the Master. Stopping off at the moon, the Master also collects the Doctor, and all three of them head into space.
But the Master's ship is intercepted by a Draconian cruiser. They are taken to Draconia and brought before the Emperor, whom the Doctor is able to convince of the Master's scheme to start a war between the two parties through the use of a device that alters the perception of others to see what they most fear. In the case of humans, they see Draconians, and the Draconians see humans.
The Master manages to escape, while the Doctor and the Draconian prince head to Earth to convince them of the plot and ease tensions. They're successful, though along the way, Jo is recaptured by the Master. The Doctor, the Prince, and General Williams are in pursuit as the Master heads to the home planet of the Ogrons.
Once there, the Doctor discovers that the plot to destabilize the galaxy through war has been orchestrated by the Master and his partners, the Daleks. The Daleks plan to invade in the chaotic aftermath of a weakened post-war atmosphere. In the ensuing battle, the Master escapes, and the Prince and the General head back to their respective governments to warn them of the plot. The Doctor, however, is injured in the fight, and Jo takes him into the recovered TARDIS, where he sends a message to the Time Lords before collapsing...
Once again, Malcolm Hulke provides some top-notch scripts that go out of their way to create realistic, nuanced characters with distinct and believable points of view. It's kind of impossible not to mention that aspect when discussing Hulke, but he also delivers a solidly entertaining and exciting space opera. Watched all in a row as classic Doctor Who often is these days, it's impossible not to see that is padded in parts, and that the Doctor and Jo's role consists largely of moving from capture to escape to recapture multiple times. However, you have to remember that it wasn't intended to be watched that way, that the series is a serial at this point, and these kinds of plotting techniques were tools of the trade. Watched in an episodic manner similar to broadcast, it's a cracking great story, with design that is a cut well above what the programme was doing at the time.
The Draconians may be the most interesting and well-designed alien races to appear on the series to this point. Far from being rampaging monsters, they are a sophisticated, culturally distinct race populated by individuals with differing outlooks and viewpoints. As if picking up on the way that Hulke wrote them, the make-up team provides some of the best work on the series in the design and application of the masks, created to give an alien appearance while still allowing for a full range of subtle emotion by keeping the eyes and mouth visible. It may not seem like much, but if the Draconians were all in full head masks, they'd come across way less sympathetically.
In contrast, the people of Earth are similarly well-developed. Hulke chooses to have a woman be the President of Earth, but doesn't make a comment on her gender, suggesting that in this future, gender roles are no longer of consequence, but doing so without a polemic. General Williams is clearly in the role of the hawk, but he's no ranting bloodthirsty caricature. Instead he's a man with an unexamined view-point, created out of necessity to deflect the guilt he feels over his role in starting a war. And once he realizes he was in the wrong, he proves himself an inherently noble man by immediately working to solve the situation.
The Master is a welcome addition to the story, not a distraction as he can so often be. His appearance is a genuine surprise, and even though one can imagine that Hulke thought the character a two-dimensional baddie, he still manages to be among the best writers for the Master. His Master has a code, and huge charm, and his presence allows Hulke to let him be the villain that the audience can hiss at, freeing him up to give the other characters more shades of gray.
Of course, this would be Roger Delgado's final appearance in the role he originated and made popular. While filming a movie in Turkey, he was tragically killed in a car accident. His death had a gigantic impact on the cast on crew, as Delgado was a well-loved member of the ensemble. You could say that his death is the moment when the Pertwee era begins its long wind-down. Others would eventually take up the mantle of the role, but Delgado's interpretation of the role set the mould for others to follow.
Frontier in Space remains a fun and exciting space opera, pulled off with style and enhanced greatly by the varied motivations of the characters.