A man, later known to be Donald Phillipson, goes for an interview in Oxford to be headmaster of a school, later known to be the Roger Bacon Comprehensive School in Oxford. At the bus stop a girl gets into conversation with him and later seduces him. She turns out to be a girl from the school, Valerie Taylor, and a year later she goes missing.
Two years after that Inspector Morse picks up the case following a road accident in which Chief Inspector Ainley was killed. A mysterious letter arrives apparently from Valerie, but Morse is convinced Valerie must be dead and tries to find out what happened on the day she disappeared. She went home from school for lunch and was last seen by a lollipop man carrying a bag. Morse discovers she was pregnant and suspects she had been sent off for an abortion.
The plot thickens when Reginald Baines, another teacher at the school, is found murdered at his house near Oxford Station. Three suspicious characters had been near his house—Mrs Phillpson, Valerie Taylor’s mum, seen wearing her distinctive cherry coloured coat, and David Acum, a French teacher who had taught Valerie’s last lesson. Morse also suspects Acum’s wife, but rejects this when he discovers she is living in North Wales and does not drive.