When singer Guy Lambert and his entourage travel from Swinging London to Antwerp on a tour, he is followed by Jill Conway, a beautiful but unworldly heiress, and Claire Dunham, a sexy society sophisticate. Complicating matters are a pair of ineptly comical jewel thieves who have hidden smuggled diamonds in Jill's luggage, a trio of bumbling Closeau-like Flemish detective, and a mysterious murderer, who seems bent on killing Jill.