* The second Doctor (Patrick Troughton), Jamie (Frazer Hines) and Zoe Heriot (Wendy Padbury) land near London in the 1960s (having noticed an alien spaceship lurking round the Moon) only to find themselves dealing with sadistic killers, specific-traitors, and a familiar implacable enemy. This episode brings back Colonel Lethbridge-Stewart (Nicholas Courtney) now a Brigadier and introduces 'UNIT' ('United Nations Intelligence Taskforce' (later renamed as the United Nations became very protective of their 'brand'). Although stretched a bit at 8 episodes, the serial moves along briskly and there is lots of action as UNIT takes on the invaders in the streets of London with small arms, grenades, bazookas, helicopters and missiles (the episode is quite militaristic). I always liked Troughton's era as the Doctor and the excitable highlander Jamie is one of my favorite companions. Zoe, petite and ever-so-cute-in-her-sparkly-cat-suit, is also a fun sidekick but, although her genius does help turn the tide when the situation seems hopeless, she doesn't seem to do a lot in this episode (both Hines and Padbury had time off when the episode was being lensed, so their appearances are somewhat sporadic). As the traitorous megalomaniac Tobias Vaughn who eventually discovers that he's out of his depth, Kevin Stoney is quite good and the series has some 'hard' moments courtesy of his sadistic operative Packer (Peter Halliday). The tension is somewhat undercut by a few out-of-place comic-flourishes (notably the Doctor hopping about and clutching the seat of his pants when being shot at), but otherwise this is a fine example of an action-focused outing from the early years of the popular sci-fi series. Like many of Troughton's serials, episodes have been lost (due to unfortunate, and I suspect now regretted, BBC policies) but the missing segments (1 and 4) have been 'recreated' using animation and original audio. The animation is not particularly sophisticated but serves to link the extant episodes and, as the first half of the story-arc is mostly set-up, we still get to see most of the 'action' in its original form.
*comments refer to the entire season 6 8-episode serial.