We’re in uncharted territory now. Doctor Who had never done a parallel universe story before, and, mercifully, it wouldn’t again until 2006. It was still new-ish enough for television in 1970, even though sci-fi writers had been tapping that well for a long, long time.
Dropping the Doctor into a universe where the good guys are all villains sounds an awful lot like the famous Star Trek episode “Mirror, Mirror” but there’s some question as to whether anybody working on Who would have had the chance to see that episode before starting work on this. It’s been suggested that Don Houghton and Terrance Dicks, as well as Trek‘s producers, were all inspired by novelists like Philip K. Dick, although I believe there were occasional episodes of The Twilight Zone that were probably the first occasions of teevee producers playing with the idea.
Since we’re all very, very familiar with the trope in the 21st Century, after a terrific chase scene, episode three of this adventure becomes almost painfully slow. It would have been incredibly important to have the Doctor talk fruitlessly about parallel universes to baddies who won’t believe him in order to get this information across to audiences in 1970. Compare that to any episode of the current Flash series. Even the first time they started screwing with alternate realities, Jesse L. Martin, playing that program’s audience identification character, understood what was going on within ten seconds and two lines of dialogue.
But then again, our six year-old is still pretty new to all this. We gave him a crash course in the concept before we watched part one – Jesse L. Martin caught on quicker – and he thought this was incredibly creepy. It’s not the green hairy men that are bothering him, it’s Nicholas Courtney, Caroline John, and John Levene being cruel and mean. He’s still not used to paying attention when the heroes aren’t onscreen, so the Pooley-Dunn-Newark-Benjamin dynamic is just random talk, but he needed all his attention to really understand what a grim situation the Doctor is in.
Incidentally, it’s often suggested that actors enjoy the opportunity that parallel universe stories present to stretch a little bit and do something different. Courtney plays a really good bureaucratic bully, and, I’m noting this here in advance for Marie to consider and watch, when he starts to crumble across the next three episodes, as all bullies do under pressure, he really shines. Doctor Who fans smile about the comfort of the eye patch and scar because it became a much-loved anecdote in interviews and convention stories, but there really is a terrific performance under that patch.