At a school attended by young boys, strange events are occurring. The masters never show up to teach class, but the boys don't think it's strange. The school itself is an architectural impossibility, but the boys don't take note of this, either. And lately, something has been visiting the school.
Haynes Junior is in the lavatory. He notices that someone is in one of the cubicles, though he didn't see anyone enter. It is the visitor, who kills him as he did Abney.
Humphreys and Karswell are in the gymnasium. Karswell climbs a rope, but Humphreys soon loses sight of him, as the ceiling of the gymnasium is impossible to see. Suddenly, bits of Karswell come raining down on Humphreys, who is found physically unharmed but psychologically traumatised.
The boys are in their physics classroom, working on their own since, as usual, the master hasn't shown up. The TARDIS materialises in front of the boys. The boys wonder if the Doctor is the physics master, but when he says he isn't, they ask him to quiz them on physics. After several questions, the Doctor asks one boy, Parkins, what year it is. None of the boys can answer him.
The Doctor talks with the boys about the school. They only now realise how strange it is that no master has come to teach them. While they are discussing it, they realise that Chiddock is not with them. The boys say he is in the refectory, but as they all head there, they hear Chiddock scream. They find his remains when they reach the refectory.
The Doctor and Parkins talk. Parkins has a theory. He imagines a society that is so far advanced that they can predict when a child will commit violent crimes decades later. They remove these children from society and arrest their development. They place them in a school where they will never age.
The Doctor has a plan to help the boys. First, he confronts the visitor, which doesn't kill him because the Doctor is psychic and it wants the boys to know why it is killing them. The Doctor says it is the corporeal expression of what would have happened if the boys had not been removed from society.
Next, the Doctor and the boys conjure up a new classmate. The creature approaches the classmate to kill it, but it changes and both entities fight. They are both destroyed.
As the Doctor leaves the school, he wonders if destroying this evil means that the boys are now sinless, or is there still evil lurking in the school.
- Fifth Doctor
- Haynes Junior
- Nyssa does not accompany the Doctor; she remains in the TARDIS, mourning Adric.
- The boys serve the Doctor orange juice and sandwiches.
- The Doctor asks the boys if they play cricket.
- All of the boys are named after characters in M.R. James' ghost stories.
to be added