A scientist's experiments with invisibility turn him into a madman.

With his face and hands swathed in bandages, and dark glasses covering his eyes, scientist Jack Griffin lets a room in a small inn in the town of Iping, England. There he attempts to find an antidote to his invisibility, the result of a secret experiment whose success has driven him away from his employer, Doctor Cranley, and fiancée Flora. The prying innkeeper's wife is terrified by Jack's apparent irrational behavior, and when she and her husband demand he leave because his rent is overdue, Jack becomes angry because their interruptions have ruined his experiment. He attacks the innkeeper and various inhabitants as he departs, eluding the police by removing his clothes and bandages and using his invisibility. He goes to the house of his associate, Doctor Kemp, who has already determined with the help of Doctor Cranley that Jack has been experimenting with monocane, a plant extract known to cause insanity. Jack intimidates Kemp, who is also in love with Flora, and appoints him to be his partner in his plans for a "reign of terror," which will ultimately result in Jack ruling the world. Jack forces Kemp to return to the tavern with him so he can retrieve his books. Jack begins to wreak havoc in the tavern just as a policeman has declared the whole "invisible man" episode a hoax. Later in the evening, while Jack is asleep, the frightened Kemp alerts Cranley and the police Jack's whereabouts. Flora insists on seeing Jack and attempts to communicate with him, but her presence incites, rather than soothes him. Outraged that Kemp has betrayed him, Jack vows to kill Kemp at ten o'clock the next night, then slips out. He goes on a murderous rampage across the countryside and finally succeeds in killing Kemp. Public terror mounts as the police are stumped as to how to capture an invisible man. One day, a farmer realizes Jack is sleeping in his barn and alerts the police, who set the barn afire to draw Jack out. Due to a fresh snowfall, they are able to follow his tracks and shoot him. Still invisible, Jack is hospitalized, and confesses to Flora that he should never have tampered with the nature of life. As he dies, he becomes visible once more.