In late nineteenth century London, young Adelaide Culver accepts her cousin Alice Hambro's dare to venture onto Britannia Mews, the squalid alley behind her family's house. Years pass, and Adelaide cannot get the mews out of her mind, feeling that her destiny is somehow bound to its rough streets. As young ladies, Adelaide and Alice are given drawing lessons by a handsome young artist, Henry Lambert, who lives in the family's old coachman's quarters in the mews. One day, Alice is unable to attend the lesson, and Adelaide and Henry, alone for the first time, acknowledge their mutual attraction. The following week, Adelaide learns that her father plans to retire and move the family to the country. She tells her parents she wishes to marry Henry, and although they object to the union because the struggling artist is not of their class, Adelaide refuses to be swayed. She goes to Henry and suggests marrying at once, but he protests that his income is inadequate to support a wife and admits that he tends to drink too much. Adelaide prevails, and the newlyweds move into the mews, where she discovers a beautifully crafted set of marionettes that Henry made years before in Paris. One day, Adelaide is summoned by her brother Treff, a student at Cambridge, who declares that their mother wants her to leave Henry and move home. Adelaide refuses, and when Henry returns from the pub, she tells him that she wants to leave the mews, leading to a bitter argument. Months pass, and with their money almost gone, Adelaide tries to persuade Henry to start giving drawing lessons again. The couple argue on the small landing outside their house, and when Adelaide pushes Henry away from her, he accidentally falls down the stairs and is killed. Her neighbor, Mrs. Mounsey, commonly known as The Sow, assures the constable it was an accident, and when she complains of financial problems, Adelaide kindly shares her remaining money with the old woman. Adelaide decides to return to her family, and writes them that Henry has died of influenza. As she prepares to leave, however, Mrs. Mounsey threatens to tell the police that Adelaide killed her husband unless she stays in the mews and makes weekly payments. Two years later, Mrs. Culver comes to visit her daughter, but Mrs. Mounsey intercepts her and says that Adelaide moved out a year ago. One night, Adelaide encounters Gilbert Lauderdale, an alcoholic former attorney reduced to addressing envelopes for a living. Adelaide rents Gilbert the coach house downstairs, and when she tells him about Mrs. Mounsey, he gets rid of the old woman by threatening to prosecute her for blackmail. Gilbert tells Adelaide that he was briefly married but has not seen his wife, who now lives in America, for years. Gilbert and Adelaide soon begin working with Henry's marionettes, and together with Desmond Bly, a puppet master, open a puppet theater. Treff comes to one of their performances, and Adelaide introduces Gilbert as "Henry Gilbert Lambert." Treff offers to be their agent, and uses his college connections in the press to make their act even more successful. Treff is troubled by the fact that Adelaide and her "husband" have separate sleeping quarters, and Gilbert makes up a story about violent nightmares that cause him to thrash and kick in his sleep. One afternoon, Gilbert's wife Milly, who has returned from America, comes to call after seeing Gilbert's picture in a magazine. She claims that Gilbert deserted her, and Adelaide sadly tells him that he must return to his wife. After Gilbert leaves, Treff arrives with the news that their parents want Adelaide and her husband to visit. Just then, Gilbert returns and happily tells Adelaide that Milly had divorced him and remarried two years before. Gilbert changes his last name to Lambert, and he and Adelaide are married that afternoon. They immediately depart for the country, where Adelaide and her family are finally reunited On Treff's advice, Mrs. Culver gives the couple separate bedrooms, but when everyone is asleep, Gilbert enters his new wife's room.