A knife for the juggler

AKA The Vengeance Man From the paperback edition's back cover: "Hambledon's most trusted man was snatched away from a crowed Paris hall -- and vanished into oblivion. With him went Hambledon's hopes of smashing the international kidnapping ring whose crimes menaced the uneasy peace of a continent. Then the missing agent reappeared with a fantastic story of an incredible conspiracy -- and Hambledon went into fast and furious action!"