A neighbor’s unexpected visit, requesting assistance for a diabetic at a nearby house, sets off the events of the film. The request isn't an invitation to a party, and the doctor "Ordway" (Warner Baxter) finds himself administering insulin before the patient dies, leaving behind only a final word as an explanation. Subsequent examination reveals poisoning, prompting police inspector "Burns" (Charles D. Brown) to advise Dr. Ordway that solving the mystery is his best defense against suspicion. His inquiries quickly become dangerous, and with each new death, unsettling figures emerge, hinting at deception and avarice. “Ordway” must rely on his intelligence to outsmart an unseen adversary while putting himself in danger (and risking his vision) as he attempts to expose the guilty party. It's a diverting film, with Baxter giving a lively performance as he probes and deceives those around him. There are many potential suspects, and the other actors perform adequately as he narrows down the list and tries to avoid trouble. The ending feels hurried, and viewers will likely anticipate developments ahead of Ordway’s discoveries, but it remains an enjoyable short drama.

Source on TMDB