A woman thinks the man who loves her is her best friend's husband.

While staying in a London hotel with his English theatrical backer, Horace Hardwick, American musical revue star Jerry Travers wakes up Dale Tremont, Horace's downstairs neighbor, with his compulsive tap dancing. Upon seeing the furious Dale, Jerry falls instantly in love and, in spite of her snubbing, daily sends flowers to her room. Then, while posing as a hansom cab driver, Jerry delivers Dale to her riding lesson in the park and romances her in a pavilion during a rain storm. Dale's loving bliss is shattered, however, when she incorrectly deduces that Jerry, whose name she has never heard, is actually the husband of her matchmaking friend, Madge Hardwick. In spite of her desire to return to America, Dale is convinced by Alberto Beddini, her adoring, ambitious Italian dressmaker, to accept Madge's invitation to join her in Italy. Before leaving, Dale encounters Jerry in the hotel and slaps him without explanation. Worried that the slap will cause a scandal, the hotel management admonishes a confused Horace, who in turn blames the incident on Bates, his quarrelsome valet. After Horace orders Bates to follow Dale, he receives a telegram from Madge saying that Dale is on her way to the Lido in Venice. Overjoyed, Jerry rushes through his London revue and flies to Venice with Horace, unaware that Dale has confessed to Madge in their hotel room that her husband has made illicit advances toward her. In Italy, Jerry continues to be baffled by Dale's emotional vacilations, while Horace is equally baffled by Alberto's threats of bodily violence. At the hotel nightclub, Dale dances with Jerry at the urging of Madge, who is unaware that Dale has mistaken Jerry, the man that she is trying to get Dale to marry, for Horace. When Jerry then proposes to Dale, she slaps him again, while Madge, who had taken Dale's initial revelations about Horace with good humor, punches her husband in the eye. Depressed and heartsick, Dale succumbs to the affections of Alberto and accepts his marriage proposal. The next day, Jerry learns that Dale has married and, by tap dancing as he did in London, connives to see her alone. Although Dale finally learns Jerry's true identity while cruising with him in a gondola, the revenge-hungry Alberto pursues the couple across the canals. Eventually Bates reveals that, while following Dale and Alberto, he had impersonated a clergyman and performed their marriage ceremony. Legally single, Dale now accepts Jerry's proposal and, back in the nightclub, dances happily with him across the floor.