The Mara was defeated, last time, by a circle of mirrors. Surely that will work a second time, right? I mean, that’s a fairly simple weakness, all told.
It may not matter. The Doctor searching for Tegan in the TARDIS doesn’t quite get what he wants, but he does have an idea, namely to check in with the locals and see if they know anything about the Mara that most people seem to think is so darn legendary. That gets him some progress but not too much. For example, Lon, the prince guy with the huge lips, he’s intrigued by all things Mara and not in a good way. Others think the whole story is an old legend, but the Doctor does acquire an interesting gemstone.
Just as well. I noted for part one that Nyssa is horrible at watching Tegan, and that’s still true. She does find Tegan, sees Tegan is acting rather evil, and not really herself. Tegan seems to snap out of it for a second and runs off, meaning Nyssa lost her AGAIN.
Nyssa is not a good babysitter.
Well, the crystal may do stuff with thoughts that the Doctor can experiment on in the TARDIS.
Tegan, meanwhile, tries to drive the Mara out with a hall of mirrors, but since the mirrors aren’t in a ring around her, it doesn’t work. She just sees herself with a snake-skull for a head. Sure, the guy running the hall opts to help, taking Tegan to Lon and infecting Lon with a second Mara or something. Then the trio head underground to find a more powerful crystal, and when they seem to find it, well, it looks like Tegan and Lon are going to kill the hall of mirrors guy with her glowing red eyes.
That’s evil and wrong. She really needs a Doctor.