Death of a Shadow — George Bellairs

Scotland Yard takes on a murder case that may have international implications . . .
 
During a police conference in Geneva, a detective named Alec Cling had been assigned to ensure the personal safety of the British minister of security. But Cling couldn't even ensure his own safety. He's been found dead in a car in the middle of a rose garden. And the car in question just happened to be hired by Superintendent Littlejohn.
 
Littlejohn is assigned to the case in London and, for once, finds that he isn't short of potential motives. The victim was a loner who seemed to hate everyone and everything, aside from children, old people, and dogs. Littlejohn is determined to crack this case before it becomes an international crisis, and sets off on a trail that leads him through a seedy hotel in Geneva, a mental clinic in the mountains, and an airport in London. Will he manage to head off disaster, or is this case simply too big for Littlejohn?
 
This is a superb British mystery from an author acclaimed for the “jolly, civilized way in which he writes a detective story” (The New York Times).