The Gorilla (1939)

A serial killer, who promotes himself as "The Gorilla", has targeted the wealthy Walter Stevens as his next victim. He climbs up the outside of his home and pins a note to this effect on housemaid Kitty. Stevens makes a call about an outstanding $250K loan, insisting he has a plan for its repayment. His plan includes his niece, Norma Denby, who is co-beneficiary with him on her father's estate. He invites her along with her fiancé, Jack Marsden, to visit. Rather than call the police, Stevens has hired an inept trio of detectives to provide protection. A second note comes: The Gorilla will strike "At midnight". To further confuse things, there is a real gorilla in a cage in the garage. Someone releases it wander around the premises. As midnight approaches, the radio suddenly comes to life and says, "five minutes" and then "one minute". Stevens disappears when the lights go out. The maid spots a hairy arm sticking out of a closet door. When it is opened, an unconscious stranger falls out. Another stranger, well dressed in dark attire, sneaks in, searching Steven's desk and hidden safe. A new message declares, "The Gorilla has done his work. Walter is dead. He's in the garage." Kitty is trapped in the gorilla cage and the gorilla, whose name is Poe, has grabbed a fainted Norma. The darkly dressed man claims to be a securities investigator. But he's really "The Gorilla". Peters, the butler, surprises him from behind. Stevens set the whole thing up to catch The Gorilla who was preying on his clients.