Neil Du Beck, the star of a remake of Song of the Toreador , receives his sixth death threat note on the last day of the picture's filming. Neil attends the preview with his co-star Claire Woodward, who is also married to their director, E. Gordon Smith. When the film ends, Claire discovers that Neil is dead in his seat, and it is later revealed that he died of poisoning. During the filming of another picture starring Claire, an actor shoots at her with a gun supposedly filled with blanks. Fortunately his aim is off, for the gun is actually loaded with real bullets. In the box of blanks, Detective McKane discovers another death threat note. McKane has the entire studio closed, allowing no one in or out until he catches the murderer. Meanwhile, Johnny Morgan, head of publicity, tries to figure out who the murderer is with his secretary, Peggy Madison, an astrology buff to whom he constantly proposes. One night he rigs a camera in his office to discover if a mouse is chewing his cigars. While they are asleep in different parts of the office, Peggy is awakened when someone sneaks in and sets off the camera. When developed, the picture shows Edwin Strange, the star of the original version of Song of the Toreador ; but Strange has been dead for eight years. Before his death, Strange was married to Claire, and it is rumored that Smith was jealous, just as he may have been jealous of Neil. Johnny and McKane suspect Smith, but he is later found hanging, with a note saying that by midnight there will be no more studio. Johnny realizes that all the props used in the murders were from the set of Song of the Toreador , and goes to Stage 13 to investigate. With the help of producer Jerome Hewitt, McKane listens in on the activities of each stage. Johnny is startled by the appearance of Strange, who confesses that after his face was damaged in a fire scene that Smith had directed, he exchanged identities with a man hit by a car, then went to live in Mexico. He resurfaced because he felt the remake would rob him of his fame. Overhearing this conversation, McKane sends detectives onto the set, and after a chase onto the roof, Strange is shot and falls to his death. The studio returns to normal and Johnny and Peggy decide to marry.