Blond Cheat with Joan Fontaine. Life is good for Mike Ashburn (Derrick De Marney). He is a senior loan officer at the Trafalgar Loan Company in London and is engaged to the boss's daughter. When closing up after work he is approached by a last minute customer who wants to borrow £400. His collateral? A pair of diamond earrings his lovely niece, Julie (Joan Fontaine), is wearing. After close scrutiny of both the niece and the earrings, Mike agrees. As the uncle quickly departs with the money, it turns out that the earrings can't be removed and Mike must keep the girl as collateral as well. Realizing that he has been swindled, Mike determines not to let Julie abscond with his collateral and vows to keep her within his sight until the uncle returns. Predictably, this causes friction with his fiancée. It turns out that breaking up his engagement is actually the intended outcome of this ruse.