The authors of this book, both of whom work for Suffolk Police, present evidence which led them to the conclusion that Jack the Ripper was an American - a man well-known in his own country, and an habitue of both high society and the underworld - who fled from London when the Whitechapel murders ceased. A team of Scotland Yard officers failed to track him down in America, and the book considers whether the police lost files in order to cover up their incompetence in letting the suspect escape. The principal evidence on which the book is based is a collection of Special Branch letters offered to one of the co-authors by a second-hand bookseller.