In the short story The Adventure of the Dartmoor Bungalow (later, chapters 3 and 4 of The Big Four), Jonathan Whalley was a former seafarer whom John Ingles had met in Shanghai some time ago. He later wrote a letter to Ingles asking to borrow some money because he needed to get out of the country to escape from "The Big Four". In the event, Whalley did not succeed in evading his pursuers and was murdered. Poirot believed that his killer was Number Four, also known as "The Destroyer".
Whalley lived in a house called "The Granite Bungalow" in Hoppator, a village on the edge of Dartmoor some nine miles from Moretonhamstead. He was about seventy years of age and drank heavily.