In Chicago, 1956, we find Leonard Burling (Mark Rylance), an English tailor running a custom shop in an area dominated by the Irish Mob, led by Roy Boyle (Simon Russell Beale). Within this turbulent world, Roy's son and second-in-command, Richie (Dylan O'Brien), along with his enforcer Francis (Johnny Flynn), utilize Leonard's establishment as a haven for illicit cash. Surprisingly, Leonard maintains this precarious arrangement since these mobsters are among his most loyal clientele.
Complicating matters further is Mable (Zoey Deutch), Leonard's shop receptionist and Richie's girlfriend, who desires to break free from their mob-controlled existence. She dreams of traveling the world, clearly stating she has no intention of following in Leonard's footsteps as a tailor or taking over his business. Mable wisely observes that to handle men like Richie, it's best to act as one of them.
Tensions rise with Richie's growing mistrust of Francis, who seems to have Roy's ear. During a fateful night, Francis brings a severely injured Richie to the shop after a clash with the rival LaFontaine family. Under duress, Leonard is compelled to treat Richie's wounds while also hiding a briefcase that contains an FBI recording detailing the crew's operations—provided by “The Outfit,” a crime syndicate established by Al Capone. After Francis departs to alert Roy, Richie expresses his belief that there's a traitor among them, suspecting Francis could be the very rat jeopardizing their operation.
Leonard, sharing a glimpse of his past, recounts his years apprenticing in a London tailor shop before moving to Chicago amidst the poverty of the post-World War I era, where expensive suits were cast aside for cheap blue jeans. When Francis later returns, Leonard cleverly intercepts him, and the two men engage in a high-stakes game of deceit over the missing tape.
The tension escalates dramatically when, amid attempts to retrieve the crucial evidence, both Richie and Francis find themselves in a deadly confrontation, resulting in Francis killing Richie. Just as Roy and his bodyguard, Monk (Alan Mehdizadeh), arrive at the shop, Leonard fabricates a story to cover for the shocking turn of events.
Roy, unwittingly embroiled in a complex web of lies, attempts to persuade Leonard of the significance of the tape that contains vital information for their organization’s survival. Leonards’ cunning facade begins to fade as he and Francis plot to outsmart each other, leading to a tragic confrontation with grave consequences.
As the chaos unfolds, Mable’s character is put to the test. Ultimately, she reveals her own duplicity, selling secrets to both the LaFontaines and the FBI, all while yearning for freedom from her mob ties. Leonard, playing a game of chess against his erstwhile customers, leverages Mable’s betrayal to hatch a cunning plan aimed at exposing the dangerous network in which they all find themselves entangled.
In a climactic twist, Leonard outmaneuvers everyone by planting false messages to mislead the mobsters all along. When the truths burst forth, it’s crystal clear that Leonard’s path has led to a pivotal showdown—he must confront Francis once and for all. As the shop goes up in flames, killing not just the past but also old loyalties, Leonard emerges, leaving behind a legacy of deceit but holding the key to a new beginning, both for himself and Mable. In a last act of escape, he becomes a phoenix rising from the ashes of betrayal and bloodshed, ready to redefine his life amidst the debris of those who underestimated him.
