In the 1960s, Richard Kuklinski (Michael Shannon) marries Deborah (Winona Ryder) and the couple have two daughters. Kuklinski keeps secrets from his family. He works dubbing pornographic films, which he then supplies to a mob operated syndicate, but he tells his family that he dubs Disney cartoons. Kuklinski is also deeply troubled. The subject of brutal beatings he received as a boy from his immigrant Polish father, Kuklinski is an emotionally disturbed and intensely violent man. In one instance a man insults him after a game of pool. Kuklinski follows the man to his car and murders him by quickly slashing his throat.
Another secret Kuklinski keeps is that his younger brother Joseph (Stephen Dorff) is serving a life sentence for raping and murdering a twelve-year-old girl. Roy DeMeo (Ray Liotta), a powerful mob boss, shuts down the pornographic film business in which Kuklinski was involved and brings him on board to work as a contract killer after Kuklinski passes an impromptu audition: killing a homeless man with Roy's gun.
During the killing of Marty Freeman (James Franco) for using DeMeo's name too freely in his business dealings, Kuklinski meets Robert Pronge (Chris Evans), another hitman for the mob. After DeMeo puts Kuklinski on suspension for allowing a teenage girl to live after witnessing a hit (Kuklinski reveals that he never kills children), he teams up with Pronge, who is a freelancer, and splits the contract payments with him in return for helping him on contract assassinations for DeMeo's boss Leo Marks (Robert Davi).
During his suspension, Kuklinski begins to show more of his anger and rage, to the extent of destroying his own kitchen while having an argument with Deborah. Kuklinski also shows paranoia when he looks at a moving ice cream truck and instantly thinks of Pronge. While distracted, Kuklinski bumps his car into another vehicle. The man he hit gets out of his car and insults Kuklinski and his family, which causes Kuklinski to enter such a raging fit that he then initiates a high speed chase after the man through three neighborhoods, again putting his family in danger.
DeMeo eventually finds out about all of this unauthorized employment after Kuklinski murders one of his associates on Leo's orders, and at the same time demands that Kuklinski sever all ties with him. Meanwhile, Kuklinski attempts to collect his $50,000 pay for the hit from Leo, but is denied the payment, prompting him to kill the mobster when he threatens his family.
Kuklinski's daughter is later seriously injured by a hit-and-run car accident. Kuklinski suspects Pronge and shoots him in a public park.
Following an undercover sting operation, Kuklinski is arrested in the year 1986. Neither his wife nor his daughters have ever suspected him of being a cold-blooded killer. Kuklinski admits to having committed over 100 vicious murders, both for personal reasons and for profit, in his 22-year career. After being sentenced to two life terms in prison he never sees his wife and daughters again. (In real life, Barbara and his daughters visited him in the hospital shortly before he died) 
As the movie ends, Kuklinski's only regret is hurting his family through the crimes he committed, and the dangers he put them in. In 2006, he dies in a prison hospital, from a rare inflammatory disease, just before he is to testify against a Gambino crime family underboss.Michael Shannon as Richard Kuklinski
Winona Ryder as Deborah Kuklinski
Chris Evans as Robert 'Mr. Freezy' Pronge (based on Robert "Mister Softee" Pronge)
Ray Liotta as Roy DeMeo
James Franco as Marty Freeman
David Schwimmer as Josh Rosenthal
Stephen Dorff as Joseph Kuklinski
Erin Cummings as Ellen
Robert Davi as Leonard Marks
Weronika Rosati as Livi
John Ventimiglia as Mickey Scicoli
Christa Campbell as Adele
Jay Giannone as Dominick Provenzano
Vincent Fuentes as JC
Ashlynn Ross as Alex
Steven Hinckley as Prison Guard
Filming took place in Los Angeles, California, New York City and Shreveport, Louisiana. Shannon's portrayal of Kuklinski includes the authentic voice Kuklinski had, as evidenced by his interviews with HBO in their 1993 documentary Conversations with a Killer.
The Iceman screened out of competition at the 69th Venice International Film Festival in August 2012. The film screened at the 2012 Toronto International Film Festival in September that year. It was released in the United States on May 3, 2013.
The Iceman currently has a score of 66% on Rotten Tomatoes.
Stephen Holden of The New York Times wrote that while the film is not "a great crime movie...it is an indelible film that clinches Mr. Shannon's status as a major screen actor." Tomas Hachard of Slant Magazine gave the film 1.5 out of 4 stars. Meanwhile, Ben Kenigsberg of The A.V. Club gave the film a C+ rating. David Rooney of The Hollywood Reporter noted that "the film's chief asset is without question its performances." Peter Bradshaw of The Guardian gave the film 3 out of 5 stars, describing it as "Zodiac meets Goodfellas". Larushka Ivan-Zadeh of Metro also gave it 3 out of 5 stars. Michael Phillips of Chicago Tribune gave it 3 out of 4 stars, commenting that the film is "sleek, purposeful and extremely well acted". Oliver Lyttelton gave the film a C rating. Chris Nashawaty of Entertainment Weekly gave the film a B- rating. Betsy Sharkey of Los Angeles Times criticized the film: "The great failing of The Iceman is not in giving us a monster, but in not making us care", she wrote. Jason Gorber of Twitch Film wrote: "Like a stiff mixed drink that doesn't live up to the quality of its ingredients, The Iceman proves to be an unpalatable, underwhelming crime drama."