Tommy and Tuppence Beresford have just become the proud owners of an old house in an English village. Along with the property, they have inherited some worthless bric-a-brac, including a collection of antique books. While rustling through a copy of The Black Arrow, Tuppence comes upon a series of apparently random underlinings.

However, when she writes down the letters, they spell out a very disturbing message: "Mary Jordan did not die naturally." And sixty years after their first murder, Mary Jordan's enemies are still ready to kill. . . .