The action occurs twelve years later on from the last novel, when Hannay, now in his fifties, is called by an old oath to protect the son of a man he once knew, who is also heir to the secret of a great treasure. He obtains help from Sandy Arbuthnot, now Lord Clanroyden, and Lombard. The action takes place in England, in Scotland and on the Island of Sheep, which is in what Buchan calls the Norlands: clearly the Faroe Islands. There are several stereotypical villains, in particular D'Ingraville from "The Courts of the Morning", and the book also focuses on Hannay's son, Peter John, now a bright but solemn teenager.