Lloyd Corrigan directs Night Key, which was written by Jack Moffitt & Tristam Tupper from a story by William A. Pierce. The cast includes Boris Karloff, Jean Rogers, Warren Hull and Samuel S. Hinds, with music composed by Louis Forbes and cinematography by George Robinson. The film centers on aging inventor David Mallory (Karloff), who is once again swindled by Stephen Ranger (Hinds), a boss of a security business. With his vision diminishing and a daughter (Rogers) he wishes to provide for before his death, Mallory decides to get even with the scheming Ranger. However, criminals led by The Kid (Alan Baxter) plan to exploit Mallory and his "Night Key" invention for their own criminal purposes. The film was produced quickly and cheaply at Universal Pictures, but it turns out to be a genuinely entertaining story. Melodrama blends with elements of science fiction as the plot develops into an engaging character study, largely driven by a theme of honesty versus dishonesty. A developing romantic subplot is skillfully incorporated by the director, enhancing the narrative’s progression while occasional action sequences prevent the film from feeling stagnant. The special effects by John P. Fulton are also enjoyable and leave a positive impression later in the story. The movie's greatest asset is Karloff’s performance. He’s an actor who deserves more recognition, and Night Key offers viewers a chance to see his capabilities beyond the horror roles that became synonymous with his career. As the somber and vulnerable David Mallory, Karloff doesn’t simply look the part thanks to makeup; he embodies the character's age through his physicality, earning considerable sympathy from the audience. His acting allows us to fully support him against the antagonists. The supporting cast also delivers solid performances: Rogers is charming, Hinds portrays a sneaky character, Hobart Cavanaugh provides comedic relief as Petty Louis, and Ward Bond makes an impactful appearance as a henchman. The story is predictable and straightforward, but with Karloff at the forefront, it’s a pleasant way to spend some time. It earns a rating of 7/10.

Source on TMDB