When American writer Max Halliday visits the very married Margot Wendice in London, he unknowingly sets off a chain of blackmail and murder. After sensing Margot’s affections for Halliday, her husband, Tony Wendice fears divorce and disinheritance, and plots her death. Knowing a former school chum is involved in illegal activities, Tony blackmails him into conspiring to kill Margot spinning a web of suspicion and deception that will tighten around them and ensnare them both in danger, recrimination, and murder.