John Osborne is a young gentleman who has left England for some, as of yet, unknown reason. He settles in Adaffia, an ends-of-the-earth type of town on the Gold Coast. Almost immediately he gets into a fight defending the only other white man in town, a drunken trader. And we see that Osborne is a tremendous fighter skilled at ju-jitsu, boxing, wrestling and strategy. These skills will come into play again and again, in a mutiny, a rebellion and other struggles with formidable opponents. His adventures at one point throw him into the company of a willful young lady who has an appetite for danger, and she and Osborne fall in love. Meanwhile back in England, „a certain Dr. Thorndyke” is investigating the crime that Osborne is supposed to have committed. This second half of the book is just as much fun as the first, involving bizarre searches for clues and meticulous examinations of minutiae, from mustache hairs to wormwood dust.