Doctor Who marathon
Terminus

Turlough’s sabotage strands the team on a leper ship. The Doctor cooperates with pirates to work out how to survive.

Another Big Bang story … didn’t we just see that in Castrovalva?

Tegan and Nyssa continue to be suspicious of Turlough. Why isn’t The Doctor? I’ve never understood that. He doesn’t even ask why an alien was hiding out in a British school. He knows he’s working for the Black Guardian. Turlough nearly gets them all killed. Constant obs would be merited.
Bit annoyed about the target being at the centre of the universe. What?

I do remember this one well because of the reveal. “We’re on a leper ship! We’re all going to die!”
(And also because Nyssa disrobes. I was 14 years old.)
Nyssa leaves the Tardis crew at the end of the story, vowing to find a cure of Lazar’s disease.

Cast notes: one of the pirates, Kari, is played by Liz Goddard of Skippy The Bush Kangaroo fame. She was also in Grandpa In My Pocket, which my kids used to watch. She was married to Colin Baker at one time.