The Iceman Cometh is set in New York in 1912 in Harry Hope's downmarket Greenwich Village saloon and rooming house. The patrons, twelve men and three prostitutes, are dead-end alcoholics who spend every possible moment seeking oblivion in one another's company and trying to con or wheedle free drinks from Harry and the bartenders. They drift purposelessly from day to day, coming fully alive only during the semi-annual visits of salesman Theodore "Hickey" Hickman. When Hickey finishes a tour of his business territory, which is apparently a wide expanse of the East Coast, he typically turns up at the saloon and starts the party. As the play opens, the regulars are expecting Hickey to arrive in time for Harry's birthday party. The first act introduces the various characters as they bicker among themselves, showing how drunk and delusional they are, all the while awaiting Hickey.
Joe Mott insists that he will soon re-open his gambling casino. The English Cecil "The Captain" Lewis and South African Boer Piet "The General" Wetjoen, who fought each other during the Boer War, are now good friends, and both insist that they'll soon return to their nations of origin. Harry Hope has not left the bar since his wife Bess's death 20 years ago. He promises that he'll walk around the neighborhood on his birthday, which is the next day. Pat McGloin says he hopes to be reinstated into the police force, but is waiting for the right moment. Ed Mosher prides himself on his ability to give incorrect change, but he kept too much of his illegitimate profits to himself and was fired from the circus; he says he will get his job back someday. Hugo Kalmar, a former anarchist, is drunk and passed out for most of the play; when he is conscious, he pesters the other patrons to buy him a drink. Chuck Morello says that he will marry Cora tomorrow. Larry Slade is a former syndicalist-anarchist who looks pityingly on the rest. Don Parritt is the son of a former anarchist who shows up early in the play to talk about his mother (Larry's ex-girlfriend) to Larry; specifically her arrest due to her involvement in the anarchist movement.
When Hickey finally arrives, his changed behavior throws the characters into turmoil. With as much charisma as ever, he insists that he sees life clearly now as never before because he no longer drinks. Hickey wants the characters to cast away their delusions and accept that their heavy drinking and inaction mean that their hopes will never be fulfilled. He takes on this task with a near-maniacal fervor. How he goes about his mission, how the other characters respond, and their efforts to find out what has wrought this change in him, take over four hours to resolve. During and after Harry's birthday party, most seem to have been affected by Hickey's ramblings. Larry who says he's done with active participation in life and is content to be a spectator "in the grandstand" pretends to be unaffected, but when Don reveals he was the informant responsible for the arrest of his own mother (Larry's former girlfriend), Larry angrily insists he doesn't want to hear it. Willie the former lawyer proposes that he'll represent McGloin in his appeal to get his old police job back as a way to brush up his own lawyering skills before he tries to get back his old job with the district attorney, and Rocky admits he is a pimp, not a bartender.
Most of the men Hickey talked with do go out into the world—dressed up, hopeful of turning their lives around—but they fail to make any progress. Eventually, they return and are jolted by a sudden revelation. Hickey, who had earlier told the other characters first that his wife had died and then that she was shot and then that she was murdered, admits that he is the one who killed her. The police arrive, called by Hickey himself, to arrest Hickey. Hickey tries to explain his murder of the woman he loved so deeply in a long dramatic monologue, saying that he did it out of love for her. He relates that his father was a preacher in the backwoods of Indiana. Evidently he was both charismatic and persuasive, and it was his inheriting these traits which led Hickey to become a salesman. An angry kid trapped in a small town, Hickey had no use for anyone but his sweetheart, Evelyn. Evelyn's family forbade her to associate with Hickey, but she ignored them. After Hickey left to become a salesman, he promised he would marry Evelyn as soon as he was able. He became a successful salesman, then sent for her and the two were very happy until Hickey became increasingly guilty following his wife's constant forgiveness of his infidelities and drinking. He then recounts how he murdered her to free her from the pain of his persistent philandering and drinking because she loved him too much to live apart from him. But, in retelling the murder, he laughs and tells Evelyn, "Well, you know what you can do with that pipe dream now, don't you?" In realizing he said this, Hickey breaks down completely. He say he must have been insane and that people need their empty dreams to keep existing. The others, now relieved that what Hickey had been telling them all throughout the play which had made them all face the truth about themselves was just the ravings of a lunatic, and so they could now safely resume believing their old "pipe dreams" and excuses about themselves and resume drinking and their old lives hanging out in Harry Hope's bar. The reaffirm their solidarity with Hickey and pledge to testify to his insanity at his murder trial, despite Hickey's desire for a death sentence. He no longer wishes to live now that he has no illusions about life.
They return to their empty promises and pipe dreams except for Parritt, who runs to his room and jumps off the fire escape, unable to live with the knowledge of what he has done to his mother after discarding the last of his lies about his action and motivation for it. He first claims that he did it due to patriotism and then for money, but finally admits he did it because he hated his mother, who was so obsessed with her own freedom of action that she became self-centered and alternately ignored or dominated him. Despite witnessing the young man's fatal leap, and acknowledging the futility of his own situation, as Larry says at the end, "Be God, there’s no hope! I’ll never be a success in the grandstand—or anywhere else! Life is too much for me! I’ll be a weak fool looking with pity at the two sides of everything till the day I die!"
