At a specified time, Tony will call, and when Margot gets up to answer, Lesgate, who will be hiding behind drapes near the telephone, is to strangle her. After Lesgate agrees to cooperate, Tony unveils his elaborate plan: On the following evening, while Tony and Mark attend the banquet, Lesgate is to watch the apartment and when Margot retires, enter using Margot's own house key, which Tony plans to sneak out of her handbag and put under the stairway carpet outside their door. As his reputation is spotless, Tony warns Lesgate that attempting to report his proposition to the police will backfire. As further enticement, Tony promises to pay Lesgate with money that he has been surreptitiously amassing through small bank withdrawals over the past year. Anticipating that she will leave him, Tony wants Margot killed before she takes off with her wealth, and blackmails Lesgate into agreeing to do the killing. Intimating that he married for money, Tony tells Lesgate that he stole Margot's letter and blackmailed her to confirm her affair with Mark. After manipulating him into meeting at the apartment to negotiate, Tony surprises Lesgate by revealing that they are former Oxford schoolmates and that he is aware of several illegal activities in which the small-time crook has been involved. Lesgate, feigning interest in a car the man is selling. In consolation, he invites Mark to his club's banquet that will be held the following evening. When Tony, a former tennis professional-turned-salesman, comes home, he announces that unexpected business matters have pre-empted their evening plans, but encourages Mark and Margot to go out without him.

Wanting a fresh start in her marriage, she is concerned about an anonymous blackmailer who stole a letter Mark wrote to her, but never picked up the money she paid or returned the letter. Several months ago, she explains, Tony suddenly became more affectionate and now, convinced that he cares for her, she plans to remain loyal, despite her love for Mark. In her London apartment, wealthy Margot Wendice discusses with her American ex-lover, Mark Halliday, why she changed her mind about leaving her husband Tony.

Unlocked by Margo Kelly