This is part of a series of reviews of Doctor Who in chronological timeline order.

Previous Story: The Merfolk Murders

I have really mixed feelings about 6 parters. They're almost always awful and dull. Just regular stories dragged out to 3 hours long for no apparent reason. It's especially boring when they're set in one location without any actual story to tell. This one isn't the worst I've done but I wouldn't say it's that good either.

The first two parts are excellent. The premise is just really interesting - the Doctor, Nyssa and Adric are trapped in a constantly evolving prison without any memories of how they got there. Tegan is on the outside, trying to break them out. When she does eventually make it in, she finds that they have no memory of her. A really great start, really suspenseful.

Unfortunately, it's quickly resolved and the team get their memories back. Then the story grinds to a halt as all 6 parters do and it turns into mindless action and running about. It just completely loses it's momentum in favour of having the characters get captured and recaptured and seperated. All the usual (boring) stuff.

It does pick back up a bit in the last part. The Doctor sends his companions away in the TARDIS and is forced to remain at the prison with three sisters. The sisters are interesting enough but I found it hard to distinguish between them. They all stay here for decades and the Doctor has to watch each of them grow old and die. It's really sad stuff and refreshingly emotional after the abysmally dull middle.

It all comes to a very abrupt end, as soon as the last sister dies the Doctor is attacked by the parasite that was plaguing the prison in the start of the story. It doesn't amount to much as the TARDIS quickly returns with no explanation of how or why the Doctor programmed it to return at this specific point beyond "the moment has been prepared for". And worst of all it leads into a cliffhanger!

This story has got some decent moments sprinkled throughout it's excessive runtime but past that it really doesn't have anything going for it beyond the excellent performances from the cast.

Next Story: The Darkening Eye