When Francis, Lord Kelton, finds a beautiful woman in his stateroom, he is flustered, but his playboy friend, Arthur, Lord Dilling, is fascinated by her. He finds out from the ship's purser that she is American widow Fay Cheyney on her way to stay in England. In London, she becomes the darling of English society, impressing everyone, including Arthur's wealthy aunt, the Duchess of Ebley, who invites her to stay with her for the weekend. Arthur tries to impress Fay, but is rejected by her, even though she is becoming attracted to him. After a charity auction at Fay's house, her "servants" look forward to a profitable future, but Charles, her butler, suggests that she may be more fond of Arthur than she pretends. Fay and her servants are really confidence operators who are planning a jewel robbery, using Fay as their front. At the duchess' country home, she suggests to Fay that Arthur, who usually acts like a cad, is really in love with her, but Fay shrugs her words off. After Lord Kelton makes a bungled attempt to propose to her, Fay sneaks into the duchess' room and attempts to steal her pearl necklace, but is interrupted by a maid. Before she can resume, Arthur also interrupts and proposes. In London, the servants worry about Fay's lack of success, while, in the country, Fay learns how to get into the duchess' safe, but finds it difficult to think of robbing her because of her kindness. Soon Charles arrives, but tells Fay that she can't get out of the plan now because of the others. Before he leaves, she decides to continue, even though Charles offers to face the others himself, and tells him that she will signal him when she has the duchess' pearls. Arthur sees Charles sneaking around the grounds and tries to have him stay the night, suspecting that he has seen Charles somewhere before, but Charles leaves. Later, when Fay steals the pearls, Arthur confronts her before she can throw them down to her friends, after remembering that he recognized Charles from an incident the previous year on the Riviera. He tries to blackmail her into spending the night with him, but she refuses, saying that she has never done that before. She then rings the alarm, rousing the entire household. He tries to take the blame, saying he acted like a cad, but she produces the pearls and tells them all the truth. When Charles arrives, he summons the police, using Arthur's name, and they wait for Inspector Witherspoon of Scotland Yard's arrival the next morning. At breakfast, Arthur reveals that a letter that Lord Kelton wrote to Fay describing his friends may have to be used in court. Though at first amused, they are shocked when they learn that Kelton has written the unexpurgated truth about all of them. Kelton then suggests that they offer to pay Fay's passage back to America in exchange for not revealing the letter's contents. Fay, however, finds the offer too "dishonorable," until Kelton finally offers £10,000. She has destroyed the letter already, though, and will not take the money. In gratitude, Kelton offers to set Fay up with a modiste shop and the others offer to be her clients, but she again refuses. Though she wants Charles to stay, he declines, saying that he would have to remain honest if he stayed with her. After offering to return Arthur's watch, which he stole five years before, he goes with Inspector Witherspoon, leaving Fay ignorant of the fact that he has turned himself in. When everyone has gone, Arthur says that he has arranged for them to be married by a neighboring bishop that morning, marking the last of Mrs. Cheyney and the first of Lady Dilling.