A Tecumseh Fox mystery.
This is one Rex wrote or at least was published in 1940. He also used the same basic story line in a Nero Wolfe mystery named The Bitter End which was first published in the November 1940 issue of The American Magazine, later in a limited edition volume by the name of Corsage: A Bouquet of Rex Stout and Nero Wolfe, and then after he had died, in Death Times Three in 1985.
This cover is a second printing Pyramid edition printed in April of 1968.
Nero Wolfe 
