Jack Moriarty was a man who claimed to be a former patient of House. Moriarty shot House, but was then shot by security as he tried to escape. House's bed was right next to his while they were recovering. It later turned out that this was a hallucination House experienced while recovering from his wounds. Not much is known about him, although like House himself he is based on a Sherlock Holmes character named Professor Moriarty who was Holmes's arch enemy.
Moriarty's wife was sick, House and his team were her doctors. In the course of diagnosing her, House convinced Moriarty that everything was relevant and he admitted to having an affair, her diagnoses had nothing to do with the affair. Genetic predisposition to brain aneurysms. House told his wife about the affair. She killed herself by closing the garage door and turning her car on.
Moriarty wanted revenge on House. He came into his office while they were diagnosing a man with a swollen tongue. He recognized Dr. Cameron, he told House that he was a former patient. Then he shot House and sarcastically said that it was shocking because no one would want to hurt him. On his way out, he was shot by security.
Moriarty was brought to the ICU right next to House. He went to talk to Cuddy. Cuddy apologized, she knew it was crazy but there was no other place, he was sedated and had cuffed to his bed. House stood over Moriarty, House unsedated him. He asked why he tried to kill him. Moriarty told him that he didn't, he needed him to live because he wanted him to suffer.
House woke up Moriarty while he was diagnosing the guy with the swollen tongue so that he could watch him save a life, he couldn't do that if Moriarty had killed him. Moriarty told House that he shot him because of his wife. Later on, House tore his stitches.
Moriarty told him what happened. He told House how his wife killed herself. He also told him that he did what he thought was right, he knew that it was his fault she died. Moriarty wanted House to admit that it was partially his fault. House noticed that a while ago, he had a hallucination.
Cameron noticed that Moriarty had been sleeping a lot, House told her that he marked a change of meds on his chart. House realized something about the patient, Chase figured it out easily. Moriarty woke up and asked him how Chase knew that. House thought he might have been getting smarter but Moriarty thought that House might be getting dumber.
Moriarty was talking to House, he appeared to be asleep. Cameron entered, Moriarty told her that House was awake because he flared his nostrils when he slept.
House had another hallucination, he yelled at Moriarty thinking that he was Wilson.
In the ICU, Moriarty told House that he wasted his life. Moriarty asked if it would have mattered if he had died. House said that it wouldn't have mattered to him because he would have been dead. House wrote something on his window. Moriarty claimed that a man's life is measured by how much tears are shed when he dies, even if House was dead he would be measured. House realized that what he wrote on the window made no sense. Moriarty continued to talk, House pictured his wife talking. Moriarty said that House was miserable for nothing and he doesn't know why he'd want to live. House apologized for his wife.
House realized that this was all a hallucination from trauma and none of it other than getting shot actually happened.
In the episode Meaning, it was revealed by Cameron that Moriarty was never caught.
In season 5, episode Painless, House writes a threatening letter under a lawyer's name and is fined. He states the last time he did this the lawyer shot him, implying a reference to when he was shot by Moriarty.
- His name was never revealed in the show, but it was shown in the subtitles for the episode No Reason.
- He shares the name of Sherlock Holmes main nemesis, James Moriarty.