Is it a murder mystery? Is it a police procedural? Is it a back-stage look at seedy French music halls? Quai des Orfevres is all of these, but more than anything else it's an amusing comedy of infidelity, jealousy and love, set in post-WWII Paris. It may be surprising that Henri- Georges Clouzot, the director of such grim films as Le Corbeau or such suspenseful nail- biters as Diabolique and The Wages of Fear, is the director of this one. Clouzot, however, was a shrewd film-maker. "In a murder mystery," he tells us, 'there's an element of playfulness. It's never totally realistic. In this I share Hitchcock's view, which says, 'A murder mystery is a slice of cake with raisins and candied fruit, a"1 )  union all select null--