Victor Trevor, an old friend of Holmes's calls him to Trincomalee, Ceylon, to investigate the vanishing of the Atkinson brothers, whose disappearance was as sudden as it was mysterious. For sixth months the people of Trincomalee have remained baffled by their departure, particularly because the brothers did not seem to have an enemy in the world. Holmes rushes to the island to help Trevor decipher just how these two men simply vanished.