Published by the British author Edward Powys Mathers, under the pseudonym of Torquemada, this literary puzzle is considered to be the hardest in the world. As you read and analyze each part of this intriguing plot, the reader finds himself immersed in an investigative and challenging suspense and is encouraged to use logic and analyze the details, in order to become a true detective. Who are the victims? And the killers? This unique novel invites you to discover. Six mysterious murder crimes and their respectiveexecutors. A series of clues and riddles carefully hidden in parts of a randomly printed plot, and only one correct order out of millions of combinations to reveal the real culprits and solve the mystery. This is the proposal of the police thriller Cain's Jawbone, by Edward Powys Mathers, whose work won the public's attention due to the incredibly enigmatic content that, almost ninety years later, reignited the fascination of readers from all around the world.