Well, that was a mess.
The long and the short of this one is Davros, unfrozen in his space prison, was asked to find a cure to a plague that was killing the Daleks. He agrees, but he also has a mind control potion that he uses to grow his own forces, and it works on both humans and Daleks. The Dalek Supreme, meanwhile, figures that out for himself, and that leads to a war between Dalek forces.
Granted, it’s really hard to tell Daleks apart, so seeing them blow each other up doesn’t help much.
And that’s not getting into the Dalek-controlled human clones. They’re looking to make one of the Doctor to assassinate the Time Lord council, but their one clone of Stien keeps breaking free of their power.
And here we are, with a lot of people and Daleks blowing each other up left and right, with the Doctor, Tegan, and Turlough passing along different points of the time corridor in and out of the TARDIS, and it sure does look like those three, and maybe the Dalek Supreme and perhaps that stray cat the Doctor almost thought was a Dalek blob in the part one seem to survive the serial. Davros tries to release the virus, looking to make a more pliable and superior breed of Dalek once he’s wiped out the old ones, but the virus also seems to take him out as well. And that was before the Doctor got to kill the old freak himself.
You know it’s bad when the Doctor is looking to kill someone.
Point is, the serial was fun to watch, but describing it would be difficult, so I won’t even try.
However, this serial is noteworthy as Tegan’s last. She abruptly, and Tegan does everything abruptly, decides to leave the TARDIS because the adventures aren’t fun anymore. Can you blame her? Everyone they met for this serial seems to have died. And, quite frankly, Tegan was always close to bolting most serials anyway. She never really had the fun other characters had, but she was still loyal to the Doctor. Her last words, to tell the since-departed TARDIS that she’ll miss the Doctor, are sincere words. She was something of the conscience of the crew, and still the most reluctant of companions I think I’ve seen in a while. That said, we’re winding up the end of the Fifth Doctor’s time, so it may be time to see a few more companions off before the Doctor himself needs another new face.
Point is, I think Turlough departs in the next one.