You know, the Black Guardian sounds a lot like Christopher Lee.
That’s kinda cool and possibly intentional.
And if it isn’t, I’m fine either way. He just sounds so deliciously evil.
To recap, there are two Brigadiers, one from 1977 and one from 1983. The Doctor (and Turlough) are with the one in 1983 while Tegan and Nyssa are in the TARDIS with the other one. In order to find the TARDIS, the Doctor needs the Brigadier to remember as much as he can about the previous encounter.
That would be a weird one where this guy with a pulsing, visible brain in his head is insisting he is the Doctor, saying he doesn’t always regenerate into a human-looking body. Tegan ain’t buying it, but Nyssa and the Brigadier are somewhere in the middle on that, figuring it’s better to be safe than sorry. This alien guy wants to go back to that ship the TARDIS almost hit before, and Nyssa can take them there, but this guy doesn’t remember Turlough, and that sort of thing makes Tegan even more suspicious.
Meanwhile, the Doctor finds the transmat pod and since there’s some communication back and forth, there’s a chance the Doctor can beam himself and his party to wherever the TARDIS is, and the Brigadier does have a part Tegan gave him. And yes, they are taking Turlough because…I don’t know, really, but he seems helpful when he isn’t being browbeat by the Black Guardian.
Oh, there is one other thing: the Brigadier is told in 1983 that he really shouldn’t meet himself because that would be bad. Since he’s a little fuzzy on whether or not he went with the TARDIS, that could be a problem.
As it is, the fake Doctor wants to explore the ship alone, asking Tegan, Nyssa, and ’77 Brigadier to stay behind. Tegan, well, doesn’t. She doesn’t believe this guy. Eventually, ’77 Brigadier wanders out himself.
Well, look, this guy with the pulsing skull is obviously not the Doctor. And Turlough finds some more guys like him in a room by themselves. So, what is going on? Well, the guy’s name is Mawdryn, and he may be, well, undead. See, he and his boys were trying to steal the secrets of regeneration from the Time Lords. And because that’s hard, he and his companions are, well, not really getting busy living or dying. They need the Doctor to somehow finish the process. There’s just one hitch.
If the Doctor does it, he will lose his own ability to regenerate.
You know, I know there are eight or nine more Doctors in the future, so I don’t see the loss of regeneration happening any time soon.