A long serving member of Basin City police department, he is a highly respected detective. He is known for being a straight cop, which is a rare thing in the confines of the crooked Sin City. He always regards others before himself and will throw himself into battle despite odds or ailments.
In fact Hartigan suffers from angina, a serious heart problem which often effects his ability to walk but never effects his aim.
He carries what appears to be a .44 Magnum revolver, an enormous hand cannon capable of removing most body parts in a single shot. He is also a strong powerful man despite his age and can still hold his own in most fights.
His love for Nancy Callahan, the girl whom he saves at age 11 and in saving her from the son of the most powerful man in Basin City condemns himself.
Hartigan first met Nancy on his last night as a detective before retirement. He was investigating a rapist and serial killer who targets young girls with his partner, Bob. Nancy Callahan was his latest intended victim. Bob requested they wait for backup (he was recieving bribes from the Roark family), but Hartigan, determined to save the girl, punched Bob out and continued on. After taking out the serial killers henchmen, Hartigan discovered that the serial killer was none other that Roark Junior, son of the most powerful man in Basin City. Hartigan shot Junior's ear off, then his hand, and finally, shot him in the groin.
Hartigan then got shot several times in the back by his partner, Bob. Hartigan tells Nancy to run, but she chooses to stay with him. Bob tells Hartigan to sit down, but Hartigan tried to reach a second gun he had in an ankle holster. Bob shot him a few more times, and Hartigan finally sat down. No longer worried about Nancy as he can hear backup nearby, Hartigan accepts his fate, as he thinks him dying so Nancy can live is a fair trade. Nancy huddled close to him as he slipped away.
A few days later Hartigan awoke in hospital, not dead. A visit from Senator Roark explained that he had paid to keep Hartigan alive, even fixing his angina, so he could make Hartigan confess to being the rapist as punishment for what he did to Junior. Senator Roark tells Hartigan that if he tells anyone the truth, he'll kill them. Hartigan does not confess, but is still sent to prison.
Hartigan spends eight years in prison, receiving letters from Nancy every Thursday, under the alias Cordelia.One thursday, however, a letter doesn't arrive. Hartigan at first thinks Nancy has finally forgotten him, however, Roark Junior pays him a visit (although Hartigan no longer recognises him because of his yellow skin and drastically changed appearance) and leaves him an envelope with a finger inside. Hartigan, assuming it is Nancy's, decides he has to get out of prison to save her. Confessing to raping Nancy and the other young girls, Hartigan gets out of prison.
Waiting for him outside is Bob, who offers him a ride into town. Hartigan accepts, not noticing Roark Junior watching him from his car. Bob tells Hartigan he made him hate himself for what he did, and that Hartigan's wife Eileen has remarried and has children. Roark Junior follows them from a distance. Hartigan and Bob say their goodbyes, and Hartigan goes to see if the only person he cares about, Nancy, is ok. Her house has been broken into, and so Hartigan goes inside. He finds books about criminal law and a little else, a matchbook from Kadie's Club Pecos. Having no other clues to her whereabouts, he travels there.
To his surprise he finds that Nancy grown up to be a beatiful young dancer at the club, and that she is in no danger at all. He then realises that he has been tricked into revealing Nancy's location. He tries to leave, but she notices him. Nancy leaps from the stage and kisses him (Marv witnesses this). Hartigan, knowing he now has to protect her, tells her to get some clothes on so they can leave.
They go outside to Nancy's car, which Hartigan offers to drive, but Nancy claims only she can keep her car running. While driving she tells Hartigan that there is a gun under the seat, but that it kicks like a mule. They are then shot at by Roark Junior, who has been tailing them. Hartigan tells Nancy to keep the car on the road, then leans out the door, and, with careful aim, manages to shoot Roark Junior in the neck, causing him to crash. Hartigan tells Nancy to stop the car, so that they can confirm the kill.
Finally after a second showdown with Senator Roark's son, Junior (who Hartigan stabs, castrates, and then pounds him in the head until he dies) Hartigan realises the only way to protect Nancy is to take his own life, which he does by shooting himself in the temple after sending Nancy back into town.
In the 2005 film adaptation of Sin City, Hartigan was portrayed by Bruce Willis.