|Only appearance||The Invisible Man|
Jack Griffin works for Dr. Cranley, assisting him in food preservation experiments alongside his friend Dr. Arthur Kemp. Griffin is deeply in love with Cranley's daughter, Flora, and the two plan to marry. Griffin is afraid he has nothing to offer her, however, and begins experimenting with an obscure and dangerous drug called monocane, hoping his work will make him rich and famous—and a worthwhile husband for Flora.
Griffin discovers a combination of monocane and other chemicals that makes a person invisible. Too excited by his discovery to think clearly, Griffin leaves Kemp and the Cranleys to complete the experiment in solitude. He injects himself with the formula over the course of a month, and became invisible. Only after he is invisible does he realize he doesn't know how to turn himself visible again.
Panicking, Griffin goes to the village of Iping and rents a room in the Lion's Head Inn, where he begins searching for a formula to reverse the invisibility. He makes himself appear visible by wrapping his head in bandages and wearing dark goggles.
Curious locals, maddening side-effects of monocane, and frustration from multiple failed tests drive Griffin insane. After he assaults Jenny Hall and severely injures her husband, Herbert, Griffin sheds his clothing to be invisible, and eludes the police. He seeks help from Kemp, but the monocane has made him so insane that he succumbs to megalomania and plans world domination with 'invisible armies'. He wants and makes Kemp his visible partner and assistant.
Not even a visit from Flora and her father helps ease Griffin's increasing insanity. He vows to kill Kemp after his old friend alerts Inspector Lane to his whereabouts, and despite intensive police protection surrounding Kemp, Griffin eventually makes good on his threats. After killing Kemp, he seeks refuge from the cold in a farmer's barn. The farmer summons police, who set fire to the barn. As Griffin flees the burning barn, the Chief of Detectives, who can see his footprints in the snow, shoots at him, the shot passing through both of his lungs.
Griffin dies from the gunshot wounds in the hospital, apologizing for his crimes, saying, "I meddled in things man must leave alone." The invisibility wears off in death, and Griffin's body becomes visible again.
The film portrays Griffin more sympathetically than does the novel. The novel's Griffin is callous and cruel from the beginning, and only pursues the experiment for wealth and his ego. In the novel Griffin stole money from his father, who committed suicide, and when the invisible man told his story to that version of Kemp he was nonchalant about his father. The novel Griffin also displayed bitterness over his abilities - he was deeply frustrated by his inability to find a way to become visible again and was prone to lash out, and when he did become invisible, he found it hard to remain invisible in the city of London because of the dirt and grime of the smoky city, with soot settling over his form risking exposure. The movie shows Griffin as an honorable man who is misguided. His insanity is purely a side-effect of the invisibility drug, and his motivation for the experiment was a misguided desire to do good for science and mankind, born primarily out of his love for his fiancée. It wasn't until his final moments he expressed remorse over the chaos of destruction he had caused.