American scientist Thomas Betterton has disappeared form a conference in Paris--only the latest in a series of notable men to vanish into thin air. Equally strange is the death of his new bride in Casablanca. To discover the secret she took to her grave, British Intelligence enlists the aide of an unlikely secret agent--an enigmatic young woman with nothing left to lose. The proposal for Hilary Craven? Impersonate the late Mrs. Betterton. But the masquerade means embarking on an unknown escapade, hiding from an unknown enemy, and retracing a stranger's steps to an unavoidable death...