As the picture shows, the Doctor is now being played by Tom Baker. But this story starts with the Doctor immediately having a flashback.
"The Doctor then had not been as he is now. He'd had checked trousers and a flute and straight brown hair cut in a fringe. He'd changed twice since then."
In his flashback the Doctor remembers the first time he met Swee the Guerner.
"Like all Guerners, he stood about four feet six, had large feet, a tortoise-like shell and a long pointed nose and, like all Guerners at that time, he had plenty to be excited about."
They were excited in the flashback because they were about to all go into space in great big spaceships to colonise another planet. They had to do this because they had nommed all the noms on their planet Rimba. The Doctor met them by accident.
"He'd been trapped in a cosmic whirlpool by the deadly stinging butterflies of Phlok, and his only means of escape was to jaunt through space and time without plotting a course. In this instance the Tardis had emerged from inter-dimensional non-space into the comforting planetary environment of Rimba."
Fortunately for the Doctor the Guerners are all very friendly. The Doctor helped Swee, his brother Kenn, and all the other Guerners into their spaceships and watched them fly off. The flashback ends and the story goes back to the Doctor and Sarah in the Tardis. The Doctor switches on the scanner and he sees Swee and other Guerners.
"It was not Swee's agitation that shocked the Doctor however, it was the fact that all the Guerners were carrying weapons, and the place that they had materialised inside looked like the old mission control building at Houston on earth."
The Doctor and Sarah leave the Tardis and are, of course, captured straight away.
I think this must be Sarah, the Doctor and Swee in this picture, because I don't know who else they could be. I wonder if Sarah is meant to be Sarah Jane Smith or if she is a new Companion not from the TV series? Anyway, back to the story.
"'Seize them!' Swee's voice was stern.
'But, Swee, don't you remember me?'
'My name is not Swee. It is Nass! We know why you've come here!'
It was useless."
Now there are two mysteries in the story - why the friendly Guerners are now unfriendly, and why Swee is called Nass and doesn't remember the Doctor.
The Doctor thinks Swee may not have recognised him because he has regenerated since they first met, but then he remembers that Swee has seen the Tardis and would have recognised that.
"Maybe Swee had never seen him before. Maybe when he had jaunted through space and time from Phlok he had landed in a time ahead of this one. Maybe his first meeting with Swee was yet to happen. He quickly checked the figures in his mind. No, the first meeting with Swee took place some twenty-three thousand years before, of that there was no doubt. So what could it be?"
I don't know what's happening in this picture at all. The mannys with big noses are Guerners, but where are they and what are they doing?
The Guerners say they know why the Doctor has come here, but they are wrong. They think he is to blame for the thing that is attacking them. Just then, it attacks again.
Cat! They are being attacked by some kind of cat! The Doctor tells them he doesn't know anything about it, but they don't believe him.
"Listen to this.' Swee turned up one of the dials on a radar screen near him. 'Our electro-voc will translate his gruntings into a word pattern intelligible to you.' Suddenly a halting, pitiless, metallic voice came out of the speaker, backed up by the sound of rending metal."
This Sto-cat sounds like a bad cat. It says:
"'Ha! Another one destroyed! Another victory for the mighty Kryptolian race. One more step on our glory trail across the universe!' There was a pause, and then the voice went on. 'You, inside the ships, you who are still alive - be ready to serve us! Be ready to work for us if you want to live! We are the masters! Now, at last, my comrades have come to activate me! We shall conquer the whole of the cosmos!'"
Even though they think the Doctor is friends with the Sto-cat they still answer his question when he asks them to tell him everything they know about the Sto-cat.
"'Well, it's a very large, four-legged robot that appears to be made of a kind of stone. How it moves I don't know, but it keeps attacking our ships.'
'And you're sure it's alone?'
'Positive. Our scanners are extremely accurate.'
'And how long has this been going on?'
Swee seemed flustered.
'How long? Why... why... for ever!'"
"The Doctor stared hard into Swee's eyes. They showed nothing but bewilderment. Finally the Doctor spoke, confidentially, but with considerable authority."
This is a clever paragraph, because we can see that the Doctor has gone from being as confused as a cat who has been confused by a confusing picture, to having solved all the mysteries of this story. He persuades Swee to trust him and he speaks to the Sto-cat using Swee's "electro-voc."
"'You say your friends have come to activate you?'
'Yes. At this moment they are activating thousands of millions of robots similar to me. Each one of us was placed on a life-support capability planet, waiting for that moment one million Brelian years later when they would come and activate us so that we may subjugate the planet and exploit whatever life has developed in that time."
The Doctor points out that none of the Sto-cat's friends are withing scanning range.
"'There must be some mistake...'"
The Doctor convinces the Sto-cat that it has been activated by the Guerners by accident.
"The Doctor continued. 'You are spoiling the plans of your creators. You are jeopardising their mission. You must de-activate. You must! Logic demands it!'"
The Doctor sounds a lot like Captain Kirk there. His persuade attempt works and the Sto-cat deactivates itself. Then the Doctor persuades the Guerners to go back into "suspended animation" and sends their ships off to another planet. He explains why to Sarah:
"'As far as I can understand it, whenever they make a journey through space while under suspended animation, all memory of their previous life leaves them. When their ships land and they awaken, they immediately adopt the role best fitted for their survival. If everything is to their liking they are friendly and optimistic. If they wake up to find themselves under attack, as they did here, they can be very nasty indeed."
Then they go down to the planet to look at the Sto-cat.
"There, lying like a cat on a wall, was a huge stone lion with a humanoid head. Sarah gasped.
'Why, Doctor... it's a sphynx!'
The Doctor nodded.
Sarah tugged at his sleeve. 'Then... then the sphynx on earth... just waiting...'
'Exactly, Sarah. The trouble is, nobody knows how long a Brelian year lasts.'"
The story ends with this picture, in which it looks as if Sarah then begins to take her clothes off. Cthulhu says this is an example of a manny's reaction to loss of Sanity. I say it is a good job the story ends when it does!