A woman pretends to be a cleaning lady to get to know her son's high-society in-laws.

Fed up with being in debt, widow Ellen McNulty hands her Jersey City hamburger stand over to the bank, intending to live in Meridian, Ohio with her son Val. There, Val, an ambitious junior executive at Kalinger Machine Tools, is ordered by the boss's alcoholic son, George C. Kalinger, Jr., to pick up Jr.'s car on the ridge where Maggie Carleton, his date of the previous evening, has left it. When Val arrives at the ridge, he is surprised to see the car dangling over the edge, with Maggie still in it. After Val rescues Maggie, who admits she accidentally backed up the vehicle too far, a smitten Val declares his undying love. Soon after, Maggie calls her globe-trotting mother Fran in Venice to announce she is marrying Val that afternoon. Val, meawnhile, receives a telegram from Ellen announcing her imminent arrival by bus. Unknown to Val, the cash-strapped Ellen has actually hitchhiked to Ohio and has been dropped off at the bus station. Ellen happily reunites with Val and is pleasantly surprised by his impending nuptuals, but quickly realizes that he is worried about her shabby clothes. Ashamed, Ellen returns the cash that Val offers her, claiming that she is flush and that the hamburger stand is being remodeled. As soon as Val departs, Ellen applies for a job and ends up missing the wedding, then in a note, tells Val that she had to return to Jersey City. Ellen actually takes several temporary jobs in order to earn enough money to buy decent clothes and an "eighteen dollar hat." Using advances on his modest salary, Val, meanwhile, begins his marriage by moving into an upscale apartment and hosting a dinner party, to which Jr., who still has feelings for Maggie, invites himself. At home, Maggie is frantically trying to prepare for the party and is relieved when Val calls and offers to send her a cook. Soon after, Ellen arrives, dressed in her new suit and flowery hat, ready to meet her daughter-in-law. Maggie, however, assumes she is the cook, and Ellen is too embarrassed to correct her, even when the real cook arrives. Instead, Ellen allows Maggie to send the woman off and heads for the kitchen. During the party, Ellen tries to get Val's attention, but he is too preoccupied to notice her until the conniving Jr. causes Maggie to dump some cake on his father and Val rushes into the kitchen for a rag. Without exposing her, Val offers to drive Ellen home, but the kindly, widowed Kalinger insists on taking her himself. Val follows Kalinger's car to Ellen's boardinghouse and, after she is dropped off, confronts her. Ellen admits all, but refuses to move in with Val, feeling strongly that no bride should have a mother-in-law under foot. At home, Val tries to tell Maggie the truth about Ellen, but she distracts him. To the newlyweds' surprise, Ellen returns the next morning and tells Maggie that Val has hired her as cook. Before Val can protest, Ellen drags him off, explaining that by continuing the deception, she can live with them without intimidating Maggie. Just then, Maggie's mother calls to announce she is on her way to visit. Upon arriving, Fran moves into the newlyweds' bedroom, forcing Val to sleep on the couch. Later, at the office, an exhausted Val discovers that Jr. has been trying to take over the important Williamson account he has been toiling on and telephones Maggie to say he has to stay late to work. When Maggie reveals that she sent Ellen to the Kalingers, Val yells at her for "loaning out" the help. Ellen, meanwhile, takes care of a sick Kalinger and informs him that Val, not Jr., is responsible for the survey that has impressed Maryland industrialist Williamson and his wife. The next day, at the Kalingers', Maggie and Val attend the party being held in honor of the Williamsons. While Val receives praise from Kalinger for his survey, Maggie plays backgammon with the condescending Mrs. Williamson. When Mrs. Williamson implies that Maggie is having an affair with Jr., Maggie becomes irate and accuses her of being small-minded. Maggie storms home, followed by Val, who demands that she call Mrs. Williamson and apologize. Maggie does so angrily, and the two part still furious at each other. Late that night, Val talks privately with Ellen, unaware that Fran is in the kitchen eavesdropping. Fran interprets their conversation about meeting secretly to discuss a hamburger stand that Ellen is thinking about buying as an arrangement for a tryst and is shocked when she sees Val kiss Ellen. The next morning, Val and Maggie make up, but as soon as Val leaves for work, Fran tells Maggie about Val's "affair." After Maggie laughingly dismisses her mother's claim, Mugsy and Annie, Ellen's unsuspecting friends, come to the door looking for Ellen. Through Mugsy and Annie, Maggie finally learns the truth about Ellen and rushes to see Val at work. Assuming that he kept his mother's identity a secret out of fear that Maggie would reject her, Maggie accuses Val of believing the worst about her and announces she is divorcing him and moving to a hotel with her mother. Later, Kalinger runs into Ellen at the factory, and she confesses everything to him. Kalinger, who is hosting a party at Maggie and Fran's hotel, brings Val and Maggie together, and Val reveals that he and Ellen are moving to Maryland to oversee the Williamson business. After Maggie insinuates that Val will not have the guts to introduce Ellen to Mrs. Williamson, Val drags Ellen to the party and asks the matron to say hello to his mother. As predicted, Mrs. Williamson acts shocked by Ellen's coarseness, but Maggie is impressed by Val's boldness and kisses him. The newlyweds then disappear into the bridal suite, while Kalinger insists on driving Ellen home.