Lora Hart (Barbara Stanwyck) applies for a job as a trainee nurse in a hospital, but is rejected by the Superintendent of Nurses, Miss Dillon (Vera Lewis) for not having graduated from high school. Fortunately, a chance encounter with the hospital's chief of staff, Dr. Arthur Bell (Charles Winninger), in an uncooperative revolving door, gets that requirement waived. Lora's roommate and fellow nurse, Miss Maloney (Joan Blondell), becomes her best friend. Lora is assigned to night duty in the emergency room. One night, Lora treats bootlegger Mortie (Ben Lyon) for a gunshot wound and earns his gratitude by letting herself be persuaded not to report it to the police as required by law. He also admires the pretty young nurse.
After she passes her training, Lora is hired for private duty, looking after two sick children, Desney and Nanny Ritchie (Betty Jane Graham and Marcia Mae Jones). She moves into the Ritchie mansion, where there is always a party going on. The children's socialite mother, Mrs Ritchie, lives in an alcoholic stupor, infatuated with the brutish chauffeur Nick (Clark Gable). When a drunken guest tries to molest Lora, Nick knocks him out. Then, when Lora turns down his demand that she pump out the stomach of a very drunk Mrs. Ritchie, he knocks Lora out and removes her to her room.
The Ritchie family physician is "society doctor" (and apparent drug addict) Dr. Milton Ranger (Ralf Harolde). Lora becomes alarmed by Dr. Ranger's treatment for the children, because she sees that they are being slowly starved to death. But she is unable to get anybody to take her seriously. She quits and takes her suspicions to Dr. Bell. He is initially reluctant to interfere with another doctor's patients, but eventually advises her to return to her job so she can gather evidence. She persuades Dr. Ranger to take her back.
Finally, Nanny Ritchie becomes so weak, Lora fears for her life and tries unsuccessfully to get Mrs. Ritchie to show any concern. By chance, Mortie is delivering liquor to the perpetual party at the mansion. Desperate, Lora sends Mortie for milk for a milk bath for Nanny, a folk remedy recommended by the frightened housekeeper, Mrs. Maxwell (Blanche Friderici). Mrs. Maxwell gets drunk and confides her suspicions to Lora. The girls have a trust fund from their late father. Nick ran over and killed their sister with his car, and (with Dr. Ranger's connivance) is deliberately starving the little girls to death. The trust fund will pass to the drunken and infatuated Mrs. Ritchie, and Nick will marry her for the money. After being threatened by Mortie, Dr. Bell shows up and examines Nanny. However, when Bell tries to take Nanny to the hospital, Nick knocks him out. Mortie stops Nick from interfering any further, and Nanny's life is saved by an emergency blood transfusion provided by Lora.
The next day, Mortie gives Lora a lift in his car. To allay her worries, he informs her that he told some of his friends that he didn't like Nick. Elsewhere, an ambulance brings a corpse dressed in a chauffeur's uniform to the hospital's morgue.Barbara Stanwyck as Lora Hart, the night nurse
Ben Lyon as Mortie, a bootlegger
Joan Blondell as B. Maloney, another nurse
Clark Gable as Nick, the Ritchie family chauffeur
Blanche Friderici as Mrs Maxwell, the Ritchie family housekeeper
Charlotte Merriam as Mrs Ritchie
Charles Winninger as Dr. Arthur Bell, director of the hospital
Edward J. Nugent as Eagan
Vera Lewis as Miss Dillon, the hospital's Superintendent of Nurses
Ralf Harolde as Dr. Milton A. Ranger, private physician to the Ritchie family
Walter McGrail as Mack, a drunk
Allan Lane as Intern
According to Robert Osborne, on Turner Classic Movies, the part of "Nick the Chauffeur" was originally intended for James Cagney, but his success in The Public Enemy prevented his accepting a supporting role, paving the way for Gable.
In July 1931, Time magazine highly praised the film and mentioned that it was well photographed, directed and acted and that the quality of the filmed story surpassed that in the original novel. The New York Times called it exciting "at times."
According to Variety, "Night Nurse is a conglomeration of exaggerations, often bordering on serial dramatics...What legitimate performances crop up in the footage seem to belong to Joan Blondell and Charlie Winninger as the hospital head. Stanwyck plays her dancehall type of a girl on one note throughout and is shy of shading to lend her performance some color."
In a 21st-century review, Eric Allen Hatch, writing for the Baltimore City Paper, said "watching [Stanwyck, Blondell, and Gable] in very early roles holds much of the appeal here, although the plot still works; a modern viewing of the film yields half high-camp value and half successful drama. Wellman would later strike gold with such films as Beau Geste (1939), but his salacious Night Nurse and hyperviolent Public Enemy were often cited in the creation of Hollywood's self-censoring Production Code. As a result of that code, this film boasts a much higher undressing-nurse-to-running-time ratio."