An expert cutter must outwit a dangerous group of mobsters in order to survive a fateful night.
Leonard (Mark Rylance), a master English tailor who's ended up in Chicago, operates a corner tailor shop with his assistant (Zoey Deutch) where he makes beautiful clothes for the only people around who can afford them: a family of vicious gangsters. One night, two killers, Richie (Dylan O'Brien) and Francis (Johnny Flynn), knock on his door in need of a favor - and Leonard is thrust onto the board in a deadly game of deception and murder.
In 1956 Chicago, Leonard Burling (Mark Rylance) is an English cutter who runs a custom tailor shop in a neighborhood controlled by Irish Mob boss Roy Boyle (Simon Russell Beale). Roy's son and second-in-command, Richie (Dylan O'Brien), and his chief enforcer, Francis (Johnny Flynn), use Leonard's shop as a stash house for dirty money; Leonard tolerates this arrangement as the Boyles and their men are his best customers. Leonard also shares a complicated relationship with shop receptionist Mable (Zoey Deutch), who is also Richie's girlfriend.Mable yearns to get out of this life in Chicago, which is controlled by the mob. Mable wants to travel the world. Mable is clear that she will never train to become a tailor like Leonard or take over the shop like he wants.Mable says that she has been around men like Richie all her life. She says that the best way to deal with them is to let them know that you are one of them.
Richie dislikes Francis as Francis has the ear of Richie's father Roy.One night, Francis shows up at the shop with Richie, who's been shot in the belly after a confrontation with the rival LaFontaine family. Leonard is forced at gunpoint to treat Richie's wounds and hide a briefcase containing a copy of an FBI recording with detailed information on the crew's operations, which was provided by "The Outfit", a nationwide syndicate founded by Al Capone. Francis gets in touch with Roy and departs, leaving Leonard and Richie alone. Richie believes that there is a rat in their organization, as the LaFontaines seem to know their every move, and believes that the recording will reveal the rat's identity. Leonard suggests to Richie that Francis is the rat.Leonard says that he used to apprentice for years at a tailor shop in London and learned his craft. He came to Chicago, as London was poor after the first world war and people could not afford the nice things in life, like the suits he stitches. Due to poverty, people took to cheap blue jeans, which became all the rage.
When Francis returns, Leonard intercepts him, claiming that Richie is light-headed and delusional from blood loss. Leonard says that Richie is fiddling with the tape and wants to know who the rat is. Francis meets Richie and says that he found a hi-tech guy who can play the tape. Francis wants to take the tape and play it to figure out who the rat is.Leonard had already convinced Richie that if Francis has the tape, he could paint anybody as the rat, even if Francis himself was the rat.
Richie wants Francis to wait till Roy gets to the shop. Francis insists that he wants to identify the rat immediately. They both struggle for the briefcase and it falls open, revealing that there was no tape inside it. Both believe the other took it.Richie threatens Francis, who kills him. He and Leonard hide Richie's body just as Roy arrives with his bodyguard Monk (Alan Mehdizadeh). The two men lie and tell Roy that Richie left the store on his own and took the tape with him; Francis volunteers to go find him.Roy starts chatting with Leonard and tells him that The Outfit is like the United Nations of the underworld. After Al Capone's death it became a network and worked to protect its members. The Outfit is considering Roy and his organization for membership. To complete the process, Roy needs to destroy the LaFontaines. That tape was provided by The Outfit to help Roy find the rat in his organization. If the tape gets out, their chances of joining The Outfit will come crashing down.The tape was made by the FBI by placing a recording device inside a hidden location and the Outfit was able to get a copy of it through their contacts.
Roy notices Richie's coat in the store's backroom and threatens Leonard. Leonard says that Richie went out threatening to kill LaFontaine.Francis then returns with Mable in tow, claiming that he found Richie's blood in her apartment and suggesting that she is the rat. When Roy orders his men to torture her for information, Leonard distracts him by revealing the reason why he came to Chicago: his wife and daughter were killed in a fire at his former shop and home on Savile Row.
The shop's phone rings and Leonard answers it; he lies that the call was from Richie, who is waiting for Roy. Roy and Monk depart but Francis insists on staying. Leonard convinces Francis to betray Roy by using Mable, who really is the rat and has been selling information to LaFontaine and the FBI. Mable had hoped that Roy and the LaFontaines would kill each other and she would be able to get away from Richie. Leonard tells Francis that he stole the tape and hid it.Roy's death at LaFontaine's hands will allow Francis to take over Roy's business. At Leonard's urging, Mable calls Violet LaFontaine (Nikki Amuka-Bird) to give her Roy's location and offer to sell her the recording. Francis hides at the back of the store when Violet arrives, intending to kill her, but Leonard warns Violet and her bodyguards shoot Francis twice instead. Mable takes the payment, and Violet leaves with the tape.
It is revealed that the night's events played out due to Leonard's manipulation. Leonard has been deceiving the Boyles by planting fake messages from The Outfit, and knew that Mable has allowed the FBI to place a bug in his store. The recording Violet took was a fake; the real one is still in the store and has been recording the night's conversations, capturing enough information to convict any remaining Boyles as well as LaFontaine. Leonard gives Mable the real tape to send to the FBI and urges her to use LaFontaine's money to live her dreams.
Intending to start over again, Leonard douses the store with flammable liquid and lights it with a match, but is interrupted when Francis gets up and tries to kill him. Leonard tells Francis that he used to be a gang enforcer like Francis, but left when he was ordered to commit a heinous crime. Fleeing from his gang, he reinvented himself and started a family, until his old gang found them and burned down his shop, killing his wife and daughter. Leonard fatally stabs Francis in the neck with his prized fabric shears. Wearing a dark jacket to hide his wounds, he quietly leaves the store as it burns.