This is an even older Doctor Who story than the Daleks' Master Plan, but fortunately for all cats and mannys not old enough to remember the days when TV was in black and white, all of this story has been kept for us to watch today.
And because it is by Terry Nation it is great! It is not as famous as The Daleks (which Terry Nation also wrote) but it is just as good in its own way, for reasons I will explain when we get to them - not all are in this episode, some are later in the story.
It starts with the TARDIS appearing on a beach. The Doctor, Ian, Barbara and Susan go out to look.
"It isn't frozen is it?" asks Barbara.
"No, impossible at this temperature. Besides, it's too warm," jokes the mischievous Doctor.
Straightaway there is mystery as a manny with flippers is following them secretly - they don't know there's somebody there, but we do.
There is also danger present because Susan is going to go into the water but she drops her shoe in and it is really acid! Barbara realises the whole sea is acid.
When the Doctor is told he says to Ian "Yes, and if you'd had your shoes on, my boy, you could have lent her hers. You mustn't get sloppy in your habits you know." Ian and Barbara chuckle at this and I did as well because the Doctor is silly. But really it is serious because they still don't know about the secret manny.
They find some vessels for going in the acid sea, so they know there are other mannys somewhere. Then Ian spots a big building.
"Look at that fantastic building!" he says.
The flippered manny is an alien, and it is following Susan now because she is on her own to get new shoes. The alien has a knife and is going to stab Susan, but it falls into a secret door with another manny behind it.
So Susan escapes without even knowing the alien was there. But then she falls into another secret door and screams. Ian and Barbara hear it and run to her, but they don't know the door is there so they can't find her. The tension has really been built up well and it is exciting now they know there is danger about.
Susan sees a manny in white robes, but in avoiding him she is caught by the alien. Then the alien dies because it has a knife in its back. This is a dramatic twist - who could have stabbed it? I think it was the manny from behind the secret door.
The Doctor, Barbara and Susan are all captured when they go inside the building. Ian finds the manny in white robes fighting with an alien and he joins in, saving the manny from being stabbed. Ian makes friends with manny so he releases the others and tells them all his story.
The aliens are the Voord and they are baddys who want to take over Marinus. The manny is called Arbitan and he is a goody who wants to use his mind control machine to make everyone on Marinus into a goody. He needs four keys to make his machine work and he tries to get the Doctor, Ian, Barbara and Susan to go and get them for him.
The next scene sees them going back to the TARDIS having said "no." We didn't see them say "no" to Arbitan but that's what they did after the last scene ended. But they can't get in the TARDIS because Arbitan has made a forcefield to keep them away from it.
He has asked them nicely and been refused, so now he is going to blackmail them into working for him. It's lucky that he explained how he was a goody earlier or this might have made him seem like a baddy.
Arbitan gives them teleport bracelets so they can go to where the keys are. Barbara teleports first, the others follow a few seconds later. Then a Voord sneaks up on Arbitan and stabs him.
The Doctor, Ian and Susan arrive where they have been teleported to, but Barbara is missing already. They find her teleport bracelet and Ian says "Look, there's blood on it!"
That is the dramatic end of the episode. A big close up on Ian's face shows this is serious business.
This is a very good beginning to the story. It is full of mystery and exciting twists, and then just when you think things can't get any better Arbitan produces teleport bracelets, which promises the rest of the story will see lots of mannys getting knocked out and losing their bracelets just like in Blakes 7!