Death in the Wasteland — George Bellairs

A murder and a missing body interrupt a getaway in the south of France . . .
 
Waldo and Averil Keelagher were looking forward to a holiday in the south of France in their new caravan. But delight turned to dismay when they discovered that Waldo's unbearable stockbroking uncle would be joining them. Not long after their arrival on the Riviera, however, they're relieved of their unwelcome guest when Waldo finds Uncle George dead in the wasteland of the Estérel.
 
Panicking, Waldo and Averil pack the body into the back of their car and rush to the nearest police station in Cannes. But things really take a turn for the peculiar when, after reporting the crime, the couple heads back to the car to find it has been stolen -- with George's body still inside.
 
Now, Superintendent Littlejohn, who happens to be on holiday nearby, finds himself caught up in one of his most complicated and unorthodox cases yet . . .