Stephen Ransome - The Men in Her Death (Panther edition)

First published in hardback in 1956 by Doubleday (U.S.) and Gollancz (U.K.). This U.K. paperback edition published by Panther (1174) is dated February 1961. Cover art is not credited, probably taken from a U.S. paperback, it seems vaguely familiar (thanks to woolrich01 for identifying it as Hillary Waugh's "The Eighth Mrs. Bluebeard).