In 2008, Niko Bellic, an Eastern European, arrives at the docks to meet his cousin Roman. Niko comes to Liberty City to pursue the American Dream, and to search for the man who betrayed his unit in a war fifteen years ago. After his arrival, however, Niko quickly learns that Roman’s tales of riches and luxury were lies concealing struggles with gambling debts and loansharks, and that Roman lives in a dirty apartment in Hove Beach rather than a mansion.
Niko defends Roman from his loansharks several times, and ends up killing Vlad Glebov, Roman’s Russian loanshark. Niko was forced to work for Vlad due to Roman’s debts but Niko killed him because he found out that Vlad slept with Roman’s girlfriend, Mallory. After Vlad’s murder, Niko and Roman are kidnapped by members of the Liberty City Bratva on order of Mikhail Faustin and his associate, Dimitri Rascalov. Faustin, not bothered by the murder of Vlad, hires Niko, who quickly learns that Faustin is a psychopath when he orders him to kill the son of Kenny Petrović, the most powerful man in the Liberty City Bratva. Dimitri then orders Niko to assassinate Faustin, and when Niko meets with Dimitri to collect on the assassination, Dimitri betrays him. When Niko meets Dimitri in an abandoned warehouse at the Docks, Dimitri brings his friend Bulgarin who claims that Niko stole from him. Niko denies the allegation saying that a cargo ship that he was transporting for Bulgarin sank and that he nearly drowned while swimming to shore.
Straight afterwards, Niko and Roman are forced to escape to Bohan when Roman’s apartment and taxi company are destroyed in arson attacks by Dimitri’s men. Unfortunately things go poorly in Bohan: one of the drug deals that Niko works on turns out to be a sting and another is busted. After the latter incident, Niko’s current girlfriend Michelle then reveals that she works for a government agency and entraps Niko into working for her agency, known only by its cover: ULC (United Liberty Paper). Niko kills several suspected terrorists for the agency in exchange for the file of the numerous crimes the police have on him and the promise of assistance in finding the traitor of his unit.
With the assistance of United Liberty Paper, Niko eventually tracks down the man responsible for his unit’s betrayal: Darko Brevic; Niko chooses Darko’s fate. In the story you’re given the option to kill him or leave him. It’s entirely up to the player and results in a different conversation between Niko and Roman on their return home. Having dealt with his past, Niko is summoned by Jimmy Pegorino, who demands one final favour after many favours: to help with an extremely lucrative deal on heroin in collusion with Dimitri Rascalov.
Niko is then faced with a choice: strike a deal with Dimitri, or extract revenge on him. This again is another choice for the player, Deal or Revenge. Choosing either of these have a massive impact on how the story concludes. However, should Niko go through with the deal, he soon finds out that Dimitri took the heroin for himself, which endangers and angers Niko. At Roman’s wedding, an assassin sent by Dimitri kills Roman with a stray bullet as Niko disarms and kills him. A devastated and vengeful Niko later tracks down Dimitri and Pegorino, witnesses the former kill the latter, before chasing and killing Dimitri. On the other hand, should Niko choose to exact revenge, Niko ambushes and executes Dimitri. At Roman’s wedding, Pegorino, furious after Niko’s betrayal, commits a drive-by shooting. He targets Niko, but ends up killing Niko’s girlfriend Kate. Niko soon tracks down, chases, and kills Pegorino on Happiness Island, who had become hated and targeted by the entire underworld of Liberty City.