June 1948. Late one night Magdalen don and author Jack Lewis hears an urgent sound like an animal scratching at the door of his college rooms. Outside is Casper Carstairs, whom the don recognises as the nervy-looking student playing Hamlet in an open-air undergraduate production that afternoon. Claiming his stepmother is out to murder him, the youth begs Lewis - one of the more approachable dons - to help him.

Plagued by writer's block as he tries to create a sequel to his first Narnian novel, Lewis semi-reluctantly succumbs to the distraction of detective work...