The one where the Doctor asks Sarah to leave...
After three very middling episodes, this fourth and final part takes a real nosedive, which is a shame considering its greater significance in the canon. Right from the outset there's some very dodgy effects on display, including the thankfully brief CSO lift down to the thermal caves, and the really cheap-looking Kastrian sets by Christine Ruscoe. Nothing looks real or solid, the finish on certain sections is ham-fisted and careless, and it all looks very unconvincing. And to top it all, Elisabeth Sladen puts in an eye-wateringly OTT performance, screaming and moaning her way through some pretty ropey writing.
The Doctor and Sarah manage to avoid a series of cheap-looking booby traps to get Eldrad to the regeneration chamber. But once activated, it appears as though Eldrad has been pulverised, yet there's one more trick up writer Bob Baker and Dave Martin's sleeves: Eldrad lives again, and is regenerated into the form of a big hulking male Kastrian. And this version has none of the elegance, beauty or eloquence of the female one. No, the male Eldrad is played by Stephen Thorne, so naturally all hope of subtlety and nuance goes out the window.