On a visit back to England, Jason finds himself with income tax problems. However, it turns out to be a way of blackmailing him into helping the police solve a series of robberies where the police computer seems to be illegally accessed.
Jason is mistaken as a hit man when he is left holding a bunch of roses at a Swiss airport after coming to the aid of a seriously ill man. To Jason's horror, the roses are soon to be exchanged for a rifle!
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.
