Plot While rehearsing a musical play in a theater, the dancer Alicia twists her ankle and the costume designer Betty drives her to a nearby hospital. However, the place is a mental institution but a doctor treats Alicia's ankle. They return to the theater but the dangerous psychopath Irving Wallace escapes hidden in Betty's car. He kills Betty outside the theater and Alicia finds her body. They summon the police and the director Peter decides to promote the play using the press and supported by the producer Ferrari. He rewrites the screenplay and casts six actors and actresses to immediately rehearse to the opening night, promising additional payment. He asks the actress Corinne to lock the theater and hide the keys. But Irving Wallace has sneaked in the theater and starts a crime spree. Will anyone survive the serial-killer?