Jack Torrance

"All work and no play makes Jack a dull boy..."

- Jack Torrance's papers in The Shining. "Heeere's Johnny!"

- Jack Torrance's famous quote after chopping down the door that Wendy was hiding in and one of the most famous movie quotes of all time.

Jonathan "Johnny" Daniel "Jack" Torrance was the main protagonist turned main antagonist in the 1980 horror-thriller film The Shining, adapted from the novel of the same name written by Stephen King.

Jack was a writer and a redeemed alcoholic who lived with his wife Wendy and his son Danny, who wielded a special psychic power known as "the Shining". Jack eventually became possessed by a demon (who, in general, had control over all of the Overlook Hotel that Jack was put in charge of) and attempted to try to kill his own family under that demon's influence.

He was portrayed by Jack Nicholson, who is also best known for portraying The Joker.

Role in the Movie
At first, Jack was the fairly likable protagonist and a loving husband and father. He was a writer who accepted the job of winter caretaker for the Overlook Hotel, despite being informed of the building's grisly past and reputation as a cursed place (which he shrugged off as a superstition) and he took his wife Wendy and son Danny with him to the hotel, and thought that the solitude of the place would help him in his writing as well.

However, Jack soon descended into madness that was never fully explained, depending on the view of the audience he could've either suffered an intense mental breakdown or he was possessed by the spirits of the Overlook Hotel—whatever truly happened to the unfortunate Jack was never fully explained. Yet, the demonic possession was further implied by all the ghosts that haunted the hotel, especially the ghosts of young kids who frequently appeared to Danny as well. The ghosts were apparently attracted by the boy's power and seemingly tried to drag him into the Underworld.

At any rate, Jack soon lost his mind completely, and became increasingly abusive toward Wendy and Danny while holding conversations with a ghostly bartender (who appeared to be the ghost of the previous caretaker) that apparently only he could see—he also had a traumatic experience with a ghastly phantom in a hotel room and ultimately descended into a murderous psychosis in which he tried to kill his wife and son with an ax (much as the previous caretaker had done years previously).

However, Jack was outsmarted by his family after a fearsome manhunt, and ultimately left to freeze to death in the giant maze outside the hotel after Wendy and Danny escaped the hotel.

Differences Between the Novel and the 1980 Film
In the original novel, it was made quite clear that Jack slowly fell under the influence of the unspeakable evil force that appeared to be the Overlook Hotel itself, or the demonic entity that took complete control of it and commanded its ghostly population. The ghost of the former bartender often appeared to Jack, and explained that he murdered his family upon the hotel's request and served as the spokesperson between Jack and the hotel, which/who tried to hire Jack as well and make him do the same.

At the end of the story, when Jack was completely controlled by the demonic entity, the narration no longer called him "Jack," but as "the creature" or "the monster." It was clearly stated that the unfortunate Jack underwent an awful metamorphosis and was no longer human. "Jack" attacked his family with a rogue mallet instead of his iconic ax and was destroyed alongside the hotel itself, which Danny, Wendy and Halloran (the cook who worked in the hotel, who also wielded the Shining) managed to destroy it by detonating the heating system.

Jack's possession was fully proven during the final confrontation between Danny and "the creature", when the boy managed to awake the spirit of his father with his Shining. Jack then bid a moving farewell to Danny and let him escape.

The Shining (1997 TV Series)
The TV series of the Shining followed directly to the novel as well as the roles of the characters and Jack.

In that version, Jack was portrayed by Steven Weber.

Trivia

 * The scene where Jack broke down the door and yelled: "Heeeeere's Johnny!" was unscripted, yet kept in the film.
 * The catchphrase "Heeeeere's Johnny!" at the time of the film's release had a doubly iconic meaning, being the introduction to the long-running host of The Tonight Show, Johnny Carson.
 * In the sequel to The Shining, Doctor Sleep, it was revealed that during Jack's days as an English professor, he had an affair with a student and she had a daughter named Lucy. Lucy would then have a daughter of her own named Abra who possessed a more potent version of the Shining. That would make Jack Abra's grandfather, and Danny Lucy's half-brother (and therefore Abra's uncle). His ghost would appear briefly to assist his granddaughter in the climax.
 * The demon that had control of the Overlook Hotel was the Greater Scope Villain because if it wasn't for the demon, Jack wouldn't have turned evil in the first place.
 * Jack starts out clean-shaven, but as he descends into madness, he grows a stubble beard to reflect this.