The Oxford Foreign Examinations Syndicate runs school exams in the Gulf and other places with an British connection. The Secretary Dr Bartlett, and Mr Roope, a chemistry don and a member of the committee disagree about the appointment of a new member of staff. Roope gets his way and Nicholas Quinn, a deaf man who lipreads, gets the job.
When Quinn is found murdered in his maisonette all the staff are under suspicion. There is Bartlett, his deputy Ogleby, the attractive Monica Height who has liaisons with some of the others, especially young Donald Martin. Strangely, nearly all of them, including Quinn, appear to have tickets for The Nymphomaniac at Studio 2 in Walton Street on the afternoon of the murder. When later, Ogleby is himself found murdered, a neat drawing of Quinn’s ticket is found in his diary.
Morse deduces which of the others is the murderer but keeps getting it wrong. An intrigue involving wealthy Arabs and prior knowledge of exam papers is clearly the cause, and Quinn had found about it and paid for it with his life.