The plot of GoodFellas culminates in a frantic, paranoia-fueled final act that details Henry Hill's downfall. After the massive Lufthansa heist, Jimmy Conway becomes consumed with fear of being caught and begins systematically murdering everyone involved in the robbery to eliminate any potential witnesses. This includes close associates, revealing the complete erosion of loyalty. Meanwhile, Tommy DeVito, who expects to be "made" into the family, is led to a room under this pretense but is instead shot in the head as retribution for his earlier murder of the made man Billy Batts. This event underscores the mob's unforgiving and inescapable code of justice.
Henry, deeply involved in a side business of trafficking cocaine against Paulie's orders, becomes increasingly erratic and paranoid due to his own drug use and the constant surveillance by narcotics officers. The climax occurs on a single, chaotic day where Henry is trying to manage a drug deal, cook a family dinner, and deal with his drug-mule babysitter, all while being followed by a helicopter. He is ultimately arrested by narcotics agents in his driveway. Abandoned by Paulie and realizing that Jimmy intends to have him killed to silence him as a loose end, Henry is left with no choice. He makes the fateful decision to become an FBI informant, breaking the mob's most sacred code. His testimony in court leads to the conviction and imprisonment of his former mentors, Paulie and Jimmy. The film's final scene shows Henry living a mundane suburban life under the Witness Protection Program. He breaks the fourth wall, speaking directly to the audience, lamenting that he is no longer a powerful gangster but just an "average nobody," a "schnook." The hidden meaning is that for Henry, the loss of his criminal life is the true punishment; he feels no remorse for his crimes, only nostalgia for the power he once wielded.