Plot
An axe murderer in Chicago kills six victims. The police, led by Inspector Gallagher with psychiatrist Dr. Immelman consulting, arrested a different man for each crime, but all of them are impervious to interrogation, lost in a state of paranoid schizophrenia. All are institutionalized.
Someone in the shadows counsels a seventh man, a bird shop owner, that he must kill dancer Edwina Brown. He hands him an axe, and the man goes after her as she walks home at night. While walking home after his play closed, actor Oliver Duffy sees the man shadowing her, intervenes and escorts her home. The man with the axe tries to get in her window; Oliver keeps watch outside her window all night, preventing another attempt near dawn.
The next day, Oliver takes measures for Edwina's safety as she returns from work, sending a taxi (with her cat in it) to take her home, and arranging a dummy figure in her bed while they wait in the other room. The bird-shop owner gets in the window and attacks the dummy with the axe; they raise the alarm, and he is captured. At the police station, he too is unreachable, obsessively rearranging slips of paper with meaningless writing on it. Oliver gives one of these to Edwina as a souvenir, and the police put her up in a hotel for the night.
When another stranger takes down the fire axe and tries to get into Edwina's room, Oliver deduces that the crimes are not random. He believes that someone is hypnotizing people to commit each murder, but his hypothesis leaves the police and Edwina skeptical. The names of all seven murderers begin with B. Edwina lived and danced in Paris, and has a secret connected with her time there, but refuses to talk about it. She, however, alleges that there would be no reason for anyone to want to kill her.
Oliver goes to the psychiatric hospital where all the arrested men are kept, and pretends to be schizophrenic to get in and investigate. He delights Dr. Immelman with his paranoid act, which gives him scope to break into his file cabinet and look under the "B"s. All seven men who did the axe murders are there, in order, as patients of another psychiatrist at the hospital, Dr. Santelle. Oliver concludes that the mastermind hypnotizing the patients must be a psychiatrist. He escapes, gets to Edwina and takes her to a seminar that will be attended by every local psychiatrist, to see if she knows any of them. She does not, but Dr. Santelle is not there.
They go to his house, and when he sees who is calling, he gets his butler to impersonate him in surgical gown and mask. Edwina thinks she does not know him. As they wait for an "L" train, someone pushes Oliver off the platform; he drops through the ties and fall to the street. As he lies, bruised, in the hospital, Edwina tells him her secret: she was engaged to someone named Cesar in Paris who left her with no word or warning. Both Edwina and Oliver then declare their love for each other.
Edwina goes to wait outside while Oliver rests, and Dr. Santelle comes in and gives him an injection. Santelle explains that he has given Oliver an overdose of insulin and he will soon die, so he might as well tell him where Edwina is. Oliver passes out without doing so; as Santelle leaves, Edwina spots him and recognizes him as Cesar. She follows him. Oliver knocks over a pitcher, a nurse investigates and a doctor saves him with a glucose injection. Oliver gets the police to go to Dr. Santelle's house, though they think he is crazy and they are saving Santelle from him.
Santelle catches Edwina, forces her inside, and reveals his reason for getting his patients to kill the seven men: he is not actually Santelle, but impersonated him to claim his large inheritance in Chicago when Santelle died in Paris. This was why he left her abruptly. All seven men who were killed had known the real Santelle. When Edwina, who knows he is really Cesar, is dead, no one will know he is an impersonator. As Cesar is about to kill her, the police arrive, and he locks her in a closet while he answers the door. The police are convinced that Oliver is crazy until one of them spots the piece of paper Edwina got from the lunatic on the floor. Cesar shoots at the police to get away, but Inspector Gallagher shoots him dead. Oliver and Edwina are reunited and plan to marry immediately.
