Working for a slick restaurateur who has fallen for her, a down-on-life songstress falls instead for a crusading crime reporter, unaware that her employer is the secret head of the city's major gambling machine racket and has a penchant for murdering anyone who gets in his way.

A Doctor's Diary is told through the eyes of Dr. Dan Norris (John Trent), resident physician in a private hospital. In his search for a cure for spinal meningitis, Norris recklessly runs roughshod over the feelings of his colleagues. The doctor's older, wiser supervisor, Dr. Clem Driscoll (George Bancroft), tries to curb Norris' impatience, pointing out that nothing takes place overnight. Angrily, Norris accuses Driscoll of malpractice and is forced to resign from the clinic -- just when a meningitis epidemic breaks out.