«Back in the Real World (Stone Angel #2)» by Marvin Albert

Pete Sawyer is a private eye of a different kind. The son of a World War II American pilot and a brave French resistance fighter, he grew up on both sides of the Atlantic — though he prefers his sun-dappled villa on the Riviera to most other places. He takes pleasure in a fine wine…and a good gun. His French name is Pierre-Ange, and it suits him. In English, it means Stone Angel.
When Pete drops by his friend Frank Crowley's house one evening, neither Crowley nor his wife Nathalie is home. Instead, Pete finds two dead bodies — and he recognizes both. One is a rival private eye. The other is Nathalie's gorgeous sister-in-law, Anne-Marie. Both are naked, with bullet holes in their heads. Were the two having an affair? Is there a connection between the murders and recent goings-on at the prestigious couture house where Anne-Marie was a star designer? Pete Sawyer must keep his wits about him — and his gun in hand — to solve this stylish mystery and keep his friend Crowley out of jail….

Don't miss the whole Stone Angel series:

Stone Angel
Back in the Real World
Get Off at Babylon
Long Teeth
The Last Smile
The Midnight Sister
Bimbo Heaven
The Zig-Zag Man The Riviera Contract