1936, London. A celebrity psychiatrist is discovered dead in his locked study. There seems to be no way a killer could have escaped unseen. There are no clues, no witnesses, and no evidence of the murder weapon. Stumped by the confounding scene, Inspector Flint, the Scotland Yard detective on the case, calls on retired stage magician turned part-time sleuth Joseph Spector. Spector has a knack for explaining the inexplicable, but even he finds that there is more to this mystery than meets the eye.

As he and the Inspector interview the colourful cast of suspects, they uncover no shortage of dark secrets - or motives for murder. And when a second murder occurs, this time in an impenetrable elevator, they realise the crime wave will become even more deadly unless they can catch the culprit soon.