In the peaceful seaside town of Broadgate, an impossible crime occurs. The operator of the cliff railway locks the empty carriage one evening; when he returns to work next morning, a dead body is locked inside – a man who has been stabbed in the back. Jimmy London, a newspaper reporter, is first on the scene. He is quick on the trail for clues – and agrees to pool his knowledge with Inspector Shelley of Scotland Yard, who is holidaying in the area. Mistrustful of the plodding local policeman, Inspector Beech, the two men launch their own investigation into the most baffling locked-room mystery – a case that could reignite Jimmy's flagging career, but one that exposes him to great danger.

When Professor Julius Arnell breathes his last in the hushed atmosphere of the British Museum Reading Room, it looks like death from natural causes. Who, after all, would have cause to murder a retired academic whose life was devoted to Elizabethan literature? Inspector Shelley's suspicions are aroused when he finds a packet of poisoned sugared almonds in the dead man's pocket; and a motive becomes clearer when he discovers Arnell's connection to a Texan oil millionaire.Soon another man plunges hundreds of feet into a reservoir on a Yorkshire moor. What can be the connection between two deaths so different, and so widely separated? The mild-mannered museum visitor Henry Fairhurst adds his detective talents to Inspector Shelley's own, and together they set about solving one of the most baffling cases Shelley has ever encountered.