Peter Cheyney 
The Man Nobody Saw 

Johnny Vallon, exchanges the dangers of total war for the equally hazardous challenges of Chennault’s Investigations. And in the heart of London, with dramatic suddenness, murder hits home—right in Chennault’s office.

Chennault, himself, owner of the flourishing detective agency, is found slumped over his desk. Heart trouble is the official diagnosis… But Vallon knows better, and proves it…