Arriving in the town of Large Mouth, John Griffen quickly becomes the talk of the town because of his strange appearance and odd behavior. His odd behavior leads a town resident named Vickie to visit him at his motel room. Griffen invites her in . Vickie notices that he was working on math, leading Griffen to tell her that it is actually chemistry, and he reveals that he was once a professor at a university. Griffen states that an accident is the cause of his appearance and his damaged eyes, and that his goggles make seeing light bearable. Griffen tells Vickie that he came to the small town of Large Mouth to focus on his work. Vickie leaves the motel after they've finished talking.
Suffering from a headache, Griffen looks at himself in the mirror, seeing a crying woman saying "John... Help me... Please..." Shocked, Griffen takes some pills and goes out for a walk. While on his walk, Griffen runs into Tommy Marvel, and tells him that he's out because he thought the fresh air would help his headache. While talking with Tommy, John is attacked by his dog, Howie. Realizing that the dog removed his glove and bandage, Griffen runs off, hoping nobody will see that his hand is invisible.
While trying to find Tommy the next day, Griffen is joined by Vickie. The two visit and talk about Tommy, Griffen telling Vickie about Tommy, the diner, and Vickie's family. Griffen reveals to Vickie that he taught at a university in Chicago. The two then spot a butterfly, and Griffen tells of how he finds them fascinating, and that they're beautiful.
Griffen begins to blend in with the town, having everyone grow used to him. About twice a week Vickie visits him, bringing food, and the two sit together and watch old movies. Griffen grows quieter, and begins to drink more, distancing himself. While alone, Griffen continues to work on his experiment and injects himself with a serum. The pattern of loneliness is finally broken when Vickie decides to visit him. Griffen states that he was just very busy with his work, and apologizes, inviting his friend in to watch a movie.
After knocking on Tommy Marvel's door, and not receiving a response, Griffen stares into the lake. His reflection appears to be normal, but it then turns into the same woman he saw in his mirror. Griffen leaps into the lake and tries to save her. Griffen wakes up to see that Tommy has saved his life. Tommy tells him that he's got a cracked head, but Griffen is still seeing things oddly and tries to return home so he can take his pills. Griffen finds Vickie and tells her that he needs help. When he gets closer to her, he sees everything in bandages. Griffen states that the serum is getting into his brain, and is helped home by Vickie. Once Griffen takes his pills, he sees Vickie as the woman in the reflections and kisses her. Vickie slaps Griffen, and he tries to apologize and asks her to stay, but she slams the door and leaves.
Hearing a knock on his door, Griffen gets up to answer it, hoping that it's Vickie. The visitor turns out to be his old partner, John Kemp. Kemp demands that they have a drink together and that Griffen give him a working formula. Griffen tells him that he'll never give him the formula, because he did all the work. Kemp threatens to reveal the truth about the woman from the reflection. Griffen states that the formula took his mind leading him to kill her, and that he loved her. Kemp begins to become paralyzed, due to the imperfect serum Griffen slipped into the whiskey he drank. Griffen smashes the bottle on Kemp's face, and proceeds to strangle him to death. With the body now invisible, Griffen drags it to the lake and dumps it there.
Because of his off behavior, when a woman goes missing, Griffen is the first person the town and the police suspect. He is questioned by Deputy Ayde, who asks him for identification. Griffen states that he doesn't have any, because he lost it. Griffen assaults Ayde, stating that he just wanted to be left alone so he could do his work and fix things. Not knowing who to turn to, Griffen runs to Vickie's house. Griffen tells Vickie that he had nothing to do with the missing woman, and that attacking Ayde was the only way out of that situation. Griffen states that he's sick, and he needs his medicine to control himself. He says that he doesn't want the town to figure out that he's an invisible man. After almost showing Vickie his condition, Vickie's dad shows up at the house. Griffen reveals his plan to take Marvel's boat across the lake, and Vickie won't let him go alone.
While Griffen tries to untie the boat, he and Vickie are caught by Tommy Marvel. After they explain themselves, Tommy allows them to use his boat, and helps cover for them. Griffen grabs Vickie and tells her that he can't let her come any further with him, and that being with him isn't safe anymore. With the sound of the argument escalating, the group that is after Griffen hears it. Griffen tells Vickie that he has to be alone. Griffen is then seemingly shot by Vickie's father, Reggie. Beneath the water he sees the woman in the reflection, removes each piece of clothing he's wearing, and reaches out for her. The town finds the body of John Kemp, thinking that it's Griffen's body. A trail of footsteps is shown leaving the town of Large Mouth, revealing that unbeknownst to everyone, Griffen is alive.