First Edition. Eric Fraser dustjacket art. Hubin listed mystery of the "biggest and fastest motor boat in the world. Its owner, Denis Halloran, used it chiefly to escape from police enquiries into his various activities on the American continent. A shrewd Intelligence Colonel enlisted Halloran in the Secret Service and [this novel] describes how Halloran and his three assistants tracked down a German spy organization". Near Fine but for foxing to page edges, in Very Good dustjacket.