When a female skeleton is unearthed by workmen digging the foundations for a library extension at St Clement's College, Gawaine St Clair, a reluctant amateur detective and former undergraduate of the college, is called in to investigate. Arriving in Oxford, Gawaine is informed that the body had been buried for 30 years, and the woman had been pregnant at the time of her death. Gawaine also discovers that a don, Richard Templeman, is missing, to be later found dead.

Gawaine's suspicions fall on men who were in college 30 years before, and are still there: Stephen Verner, who was then about to marry a socially advantageous woman; Father Gerard, the celibate college chaplain; Heatherington the creepy head porter; Colonel Morrison, the Bursar, who appears to have no motive; Dr Porteus, whose Fellowship depended on his unmarried status.

A letter gives Gawaine clues to the identity of the woman and her lover, and he finally finds the killer. But is he right? And will he survive long enough to prove it?