After Slip Mahoney and Horace Debussy "Sach" Jones, who work for a New York laundry service, crash their delivery van, they are fired. The boys convince Louie Dumbrowsky to allow them to use a back room of his sweet shop to set up Slip Mahoney Enterprises and install several washing and drying machines, supplied by the company at which their friend, Gabe Moreno, is employed. One day, a young widow, Laura Andrews, abandons her baby in one of the laundromat's baskets. Later, Hope and Faith Andrews, the aunts of Laura's late husband, bribe a doctor to have Laura committed to a sanitarium, stating that she is deteriorating mentally. When the police bring Laura home, however, she claims that Hope and Faith have been trying to drive her crazy for some time and refuses to tell them where she has left the baby, who is entitled to inherit his late grandfather's estate. Meanwhile, the boys have found the baby and are trying to feed him, but he rejects Louie's offer of hamburger and fries. "Bananas," a mobster and one of the boys's acquaintances, discovers from a newspaper headline that the baby is the missing Andrews heir and proposes to his boss, Cherry-Nose Gray, that they pick up the $25,000 reward. They visit the Andrews sisters, who as students of criminology recognize them as gangsters and even have files on them. The sisters, who can control their brother's fortune if Laura is not around, offer them $50,000 to keep the baby out of sight for a few days. Cherry-Nose shows Slip the newspaper and asks the boys to hold the baby in return for some cash. Inadvertently, Slip then signs a ransom note, which Cherry-Nose keeps as "insurance." Later, Burton, a police patrolman, visits the sweet shop and hears the baby crying, but the boys manage to fool him. After Slip reads in a newspaper that Laura has been committed to Midvale Sanitarium for special treatment, he decides to visit and quiz her. Slip takes Sach along, but is forced to register him as a disturbed patient. Posing as a myopic psychiatrist, Slip locates Laura and tells her about her baby's whereabouts. Meanwhile, Sach wanders around, finds the operating room, which he mistakes for a toy shop, and begins removing many items until he is interrupted by two doctors, who regard him as a very interesting specimen and prepare to operate on him immediately. After Slip hears Laura's account of the problems with her aunts, he finds Sach in time and they all escape. When Slip and Sach return to the sweet shop, they discover that Cherry-Nose is holding the other boys and the baby prisoners. Slip and Laura try to leave for the Andrews estate, where Andrews' will is about to be read, but are stopped by Cherry-Nose and his men. Gabe comes to their rescue and a brawl breaks out until Burton and another officer arrive. Meanwhile, at the Andrews estate, Hope and Faith listen as the lawyer reads their brother's will, which leaves everything to his grandson, providing he and his mother are present at the reading of the will. If they are not present, his estate is bequeathed to the sisters. After the lawyer opens a chest and discovers three million dollars inside, Hope prepares to sign for receipt of the money, when Slip, Sach, Laura and the baby arrive and confuse the lawyer. Hope draws a gun while Faith takes the chest, but they are prevented from leaving by the arrival of Burton and the other boys. Later, Sach resumes talking to a glamorous wax dummy with which he has become infatuated, and to Slip's consternation, she comes to life and walks off with Sach.