Sheltering from the rain while out for a walk in north London one September evening, trainee doctor Humphrey Jardine happens upon the body of a dead man, only for the corpse to have vanished by the time he is able to bring the police to the location. Before long, a discovery at the scene of this vanishing, a chance encounter with the comely Miss Sylvia Vyne, a suspicious clergyman, and the death of an elderly patient just as Jardine is about to act as locum tenens for another doctor’s practice will combine with this mobile corpse to make quite the most “astounding sequence” in young Jardine’s life, changing it forever.

Summoned one evening to the house of a bedridden man — and taken there in a carriage with blacked-out windows to obfuscate the location — Dr. Christopher Jervis suspects poisoning but is assured by the people looking after Mr. Graves that no poison could have been administered. Some weeks later, he is summoned a second time and, after administering some treatment that sees Mr. Graves begin to revive, is dismissed and never hears of the patient or his carers again. Between these two visits, however, Jervis consulted Dr. John Thorndyke, which proves to be most fortuitous when further investigation into the matter becomes important.