Scobie Malone, a detective sergeant in the bush country of Australia, is sent to London by Flannery, his ambitious supervisor, to arrest Australian High Commissioner Sir James Quentin for the murder of his first wife 25 years ago. Scobie meets Quentin in London and is impressed with his personable manner and dedication to a vital trade conference he is directing. Unperturbed by the murder charge, Quentin refuses to leave until the conference is over. Scobie moves into Quentin's house and meets Sheila, Quentin's second wife, and Lisa, his devoted secretary. When Quentin is called away to visit the ailing American ambassador, he is accompanied by Scobie, who saves him from an attempted assassination. That night, Scobie is summoned to a gambling club where he meets the beautiful Madame Cholon, spends the night with her, and is beaten by three thugs on his way home. The next day at Wimbledon, Scobie saves Quentin's life again when Pallain, a news reporter, tries to shoot him. Sheila discovers the reason for Scobie's visit and confesses that she killed Quentin's first wife, although Quentin insists that she is lying. The butler then informs Sheila that he has placed a bomb in the living room at the instruction of Madame Cholon, who is a foreign agent sent to disrupt the trade conference. To save her husband's career, Sheila takes the bomb to Madame Cholon and remains with her until it explodes.