Richard Hannay is pulled from his quiet retirement when a long-standing oath forces him to protect the son of an old comrade from a lethal conspiracy. Living a settled life in the English countryside, Hannay finds his peace disrupted by the arrival of a mysterious request linked to a past promise made in Africa. He must navigate a web of danger involving hidden treasure and a persistent blood-feud that threatens the safety of those under his protection. The narrative follows Hannay as he gathers allies and moves across the landscape, eventually reaching the isolated Island of Sheep to face his adversaries. The story utilizes a classic adventure framework, emphasizing the protagonist's resourcefulness and the shifting geography of the British Isles.

Readers and critics often discuss this work as a poignant conclusion to the Richard Hannay series, noting how it balances traditional action with a more reflective tone. Discussion frequently centers on the author's ability to evoke the rugged beauty of the Scottish landscape, which serves as a backdrop for the final confrontation. Many highlight the novel's significance as a bridge between the classic adventure stories of the early century and the changing literary landscape of the 1930s. Critics often point to the character development of an aging Hannay as a key element that distinguishes this entry from earlier, more kinetic installments in the series.