As a student reporter Nancy investigates a murder case, believes the arrested woman is innocent, and uncovers the murder conspiracy.
City editor Bostwick (Thomas E. Jackson) gives students trivial stories to cover. Nancy Drew (Bonita Granville) goes to a coroner inquest. Eula Denning (Betty Amann) is questioned about poison and the will that makes her the heir; she says she did not do it but is charged. After her car is bumped, Nancy follows Soxie Anthens (Jack Perry) to the Lambert house. Bostwick tells Nancy they already published the story. Nancy asks her father Carson Drew (John Litel) to defend Eula. Nancy's car smokes because of a prank by Mary Nickerson (Mary Lee) and Killer Parkins (Dickie Jones). Nancy gets Ted Nickerson (Frankie Thomas) to help her and gives him a hat. At the jail Nancy gets Ted to take a photo of Eula, who tells of the missing poison can. Ted distracts the guard so that Nancy can sneak into the Lambert house. She finds the can but is chased by Soxie. She goes to the police but is followed by Soxie and Bonnie Lucas (Sheila Bromley), who grabs the can and runs. Nancy runs after her but knocks down Captain Tweedy.
Nancy tells her father that she promised he would defend Eula. He agrees and puts her to bed. Nancy learns that the man is boxer Soxie Anthens and tells Ted to pose as a boxer. Nancy gets Soxie to call his girl-friend and records the number. Ted spars with Soxie and is knocked out. Nancy has Ted call, and they learn her name is Bonnie Lucas. At a Chinese restaurant Nancy sees Bonnie with Miles Lambert (Larry Williams) and calls Soxie to tell him. Soxie comes in and quarrels with Miles, hitting him. Nancy learns from her father the estate goes to Miles if Eula is convicted. Mary ordered food, and they can't pay. Instead of washing dishes, Mary sings with Killer, Nancy, and Ted. Nancy gives Bostwick the story that her father has evidence to clear Eula, but she tells Sergeant Entwhistle (Olin Howlin) that is false but is a trap to catch Soxie and Bonnie. Disguised as an old lady, Entwhistle checks into the hotel. He, Ted, and Nancy wire two rooms. Miles finds Entwhistle in his room and knocks him out. With a gun he makes Ted and Nancy go on the roof. Trapped, Nancy and Ted pull fuses to alter the sign. They get out and see Soxie go into Miles' room. They listen as Miles implies he hired Soxie for the murder. Soxie and Miles flee in Nancy's car; but Mary and Killer have caused it to smoke, and they are caught.
Once again the youthful Nancy uses various devices to
follow the clues she luckily finds so easily. Journalism proves
to be a useful entry into crime investigation.