Joseph Smith, a fugitive ex-Special Forces soldier and a homeless drunk in London, is attacked and chased by a group of thugs one night, and finds himself breaking into an apartment. Learning that the owner, a successful photographer named Damon, won’t return till the first of October, Joseph starts squatting there and assumes a new identity, calling himself Joey Jones and using Damon’s resources while looking for his homeless friend Isabel who been coerced into becoming a prostitute by the same gang that attacked him. Joey is friends with Sister Cristina, a Polish nun who runs the local soup kitchen, and helps him with antibiotics for the wounds he received in the fight with the thugs and information on Isabel’s whereabouts. To deflect suspicion of Damon’s neighbors, he tells them that he is Damon’s boyfriend and starts working at a Chinese restaurant. One night at work, when some rowdy diners cause a scene, Joey fights them off outside the restaurant. His fighting skills impress the senior manager Mr. Choy, who is connected to a London Chinese organised crime syndicate; he hires Joey as a driver and enforcer, tasked with collecting extorted payments and delivering drugs. He saves some of the money he receives and begins ordering pizzas for the homeless at the soup kitchen and buying gifts for Cristina. He finds Dawn, his ex and mother of his young daughter, and gives her some money.
Joey learns from Cristina about Isabel’s murder as she hands him over photographs of her corpse in the river. An enraged Joey confronts the same thugs who beat him up earlier, and through interrogation acquires a rough description of the killer. In order to pass on the information to Cristina, Joey invites her to an art gallery where she gets drunk, opens up to him and reveals she used the money given by him to buy tickets for a ballet set to happen on the same date as Damon’s scheduled return. Joey, on the other hand, violently attacks a restaurant owner to extract money. Learning of this, the police question Cristina who lies to them. While driving her home, Joey learns she was sexually abused as a kid by her gymnastics instructor due to which she killed him. Being too young, she was sent to a convent instead of prison. Feeling distracted due to her relationship with Joey, she asks for a transfer to Africa. Mr. Choy’s boss helps Joey track down the killer in exchange for driving a truck containing boxes of Chinese people being smuggled into the UK. Joey finds out about the killer named Max Forrester, a man who assaults prostitutes, through an invitation to a rooftop cocktail party on the first of October, provided by a prostitute.
On the first of October, Cristina tells Joey she will soon leave for Africa and the two consummate their relationship as Damon returns. Fleeing through the fire escape with Joey, Cristina invites him to the ballet. Joey delivers a bag full of money to his ex and daughter along with his photos, and goes to the rooftop cocktail party where he kills Max by throwing him down the building. Joey runs away and is found sleeping near a curb by Cristina after the ballet ends. Waking up, Joey reveals he’s on the run from a court martial for random revenge killings he carried out in Afghanistan for the deaths of five of his men, who were slaughtered in front of him in their armored vehicle. He often has random hallucinations of the men he killed and of “hummingbirds”, the aerial drones in Afghanistan. The next day, Cristina receives a note from Joey while leaving for Africa. It reveals Joey paid his debts to everyone including Damon, has informed the police about Mr. Choy’s human trafficking operation, and would now disappear into the streets once again. As a drunk Joey walks into the streets, he is being pursued by the police with the help of the drones similar to the “Hummingbird”.