Jason falls under the hypnotic spell of two glamorous thieves, Claudia and Elaine. Claudia steals from him the only copy of his recently completed film script, and she and Elaine demand that, for its return, he pose as an expert in ancient manuscripts in order to steal the Constance Missal, a valuable document recently acquired by the British Museum. He is to authenticate it for one Lord Barnes, but his lordship is also planning to obtain the Constance Missal for himself.