Movie - Secret of the Blue Room (1933)

 

At her family's rural manor in Germany, Irene von Helldorf celebrates her twenty-first birthday with her father Robert, her suitor Thomas Brandt, and Thomas's two rivals, Walter Brink and Frank Faber. Thomas challenges Walter and Frank to each spend a night in a mysterious locked blue room in which several murders had occurred years before, each at exactly one hour past midnight. The first victim was Robert's sister, followed by his best friend and, later, a detective who attempted to solve their deaths. Thomas sleeps there on the first night but disappears exactly at 1:00 a.m.

Irene explores the blue room alone the following day, but is attacked by an unseen assailant and loses consciousness, regaining it with no memory of her attacker's identity. Frank agrees to spend the night in the blue room after Robert retires for the evening. Frank begins playing a piano in the room shortly after midnight to signal to the others that he is still alive. Unable to sleep, Irene is comforted by Walter before a gunshot rings out, and the piano playing ceases. Walter rushes to the blue room, where he finds Frank shot to death.

Walter reports Frank's murder to Commissioner Forster. Moments later, an alert buzzer sounds from the blue room. Walter enters the room to find a cat has triggered the buzzer, but cannot explain how the animal accessed the room. The next morning, the Commissioner and his assistant Max question the von Helldorfs and their guests, along with Mary and Betty, servants of the manor, and Paul, the butler. Betty tells the Commissioner that she saw a strange man exit the blue room after Frank's murder.

The next day, an apparent vagrant enters the manor, and Robert confesses to the Commissioner in confidence that the man is his brother, who is in fact Irene's biological father. On the fifth night, the Commissioner oversees the manor while Walter stays in the blue room, hoping they can apprehend the killer. Walter places a dummy in an armchair in the blue room and hides behind a coat. At exactly 1:00 a.m., the assailant breaches the door to the blue room and aims a revolver at the dummy before firing.

The cloaked assailant flees into an underground corridor system that runs beneath the manor, with Walter and the Commissioner's officers in pursuit. Following a gunfight, the killer is apprehended and revealed to be Tommy. Tommy confesses to killing Frank and plotting Walter's death out of jealousy, believing both men were threats against his relationship to Irene.