Meanwhile, Alleyn's celebrity painter wife Agatha Troy has just successfully launched her latest exhibition and, on a whim, takes a canal cruise on the MV Zodiac through 'Constable' country.

Her fellow passengers are, of course, the usual assorted bunch of suspects, when the murder takes place of Hazel Rickerby-Carrick, a needy, tiresome spinster whose diary is her "self-propelling journal" and who indiscreetly boasts of carrying around her neck a fabulous Fabergé, jewelled zodiac ornament, which is, of course missing.

The passengers, all suspects, include: a literary lepidopterist clearly much smitten by Troy, a pair of gushing American tourists in search of antiques, a sporting Australian clergyman, a London slum landlord with a talent for fine graphics and, finally, a grandly exotic and distinguished surgeon of Afro-European origin, to whom Troy is greatly attracted, and who is the subject of overt racism from several of the passengers.

The plot develops around a conspiracy to plant fake Constable paintings in the international art market, and, Alleyn arrives hot-foot to protect his wife, solve the crime, unmask and arrest 'The Jampot' [who?]

"[1] The Illustrated London News took the same tone: "Miss Marsh has captured the ambience of life on an 'inshore liner' with her usual flair...