NIGHT KEY (1937)--colorized

Night Key is a 1937 American science fiction crime film starring Boris Karloff and released by Universal Pictures

Plot
The inventor of a burglar alarm attempts to get back at the man who stole the profits to his invention (Hinds) before he goes blind. The device is then subverted by gangsters who apply pressure to the inventor and use his device to facilitate burglaries.
Cast

Boris Karloff - David Mallory (billed as Boris Karloff)
Warren Hull - Jimmy Travis (billed as J. Warren Hull)
Jean Rogers - Joan Mallory
Alan Baxter - "The Kid"
Samuel S. Hinds - Stephen Ranger (billed as Samuel Hinds)
Hobart Cavanaugh - "Petty Louie"
David Oliver - "Mike"
Ward Bond - "Fingers"
Frank Reicher - Carl
Edwin Maxwell - Kruger