Plot

When a notorious criminal is forced to return to London, it gives a detective one last chance to take down the man he's always been after.

Former criminal Jacob Sternwood is forced to return to London from his Icelandic hideaway when his son is involved in a heist gone wrong. This gives detective Max Lewinsky one last chance to catch the man he has always been after. As they face off, they start to uncover a deeper conspiracy they both need to solve in order to survive.—Anonymous

Welcome To The Punch relates the story of a former English criminal Jacob Sternwood (Mark Strong), who comes out of hiding in Iceland, in an effort to save his son Ruan Sternwood (Elyes Gabel) when a heist goes wrong. Sternwood is the one man that London detective Max Lewinsky (James McAvoy) has always been after. During their cat-and-mouse game, the two become unlikely allies, working together to expose a deeper conspiracy.

Jacob was a robber in London & Max was assigned his case. Max almost managed to arrest Jacob, but Jacob shot Max in the leg & escaped. 3 yrs later Ruan is on an airplane, shot in the abdomen when he runs & jumps of the stationary aircraft & makes a call to Jacob, before he is arrested. The newspapers describe Ruan & his accomplice (Otis Blake) to be involved in gun crime, when they were shot by the police.

Max & Sarah Hawks (Andrea Riseborough) are partners. They have arrested Dean Warns (Johnny Harris) in connection with the Otis Blake shooting at the docks, but he is allowed to walk by Max's seniors Commander Thomas Geiger (David Morrissey) and DCI Nathan Bartnick (Daniel Mays) as Warns alibi holds up & the witness who claimed to see Warns at the docks, retracts his statement. Max finds out that the kid arrested at the airport is Ruan, son of Jacob. Max personally takes control over Ruan's guard as he knows Jacob will show up. But Ruan dies of a cardiac arrest. Karen Edwards (Danielle Brent) is a press reporter & is leading Thomas's campaign to become the Mayor of the city on the promise of controlling gun crime.

Jacob visits the hotel where Ruan was staying & finds a bloody shirt & a sack of money hidden in the AC vent. Jacon uses his underworld connections to advertise that Ruan was staying at the Gregomar hotel. Max finds that the Warns witness was given money to retract his statement. Max hears the word on the underworld & arrives at the Gregomar hotel where Jacob has just killed an intruder & escaped. One of the intruders was Bartnick & the other was another cop (Harvey Crown). Max finds Harvey dead & figures that the 2nd intruder was Bartnick, through his glasses that were left behind at the hotel. Meanwhile Sarah follows Warns, without telling Max. She finds Warns at the docks in a shipping container. She searches at night & finds the container & is horrified at its contents. Warns finds Sarah snooping & kills her.

Jacob calls Bartnick, who fixes a meeting to "explain who shot Ruan". Thomas calls Max & tells him about the meeting between Batrnick & Jacob & sends him there. Once at the location Jacob & Max are attacked by Bartnick & Warns. Bartnick is killed & Jacob & max escape. Max tells Jacob that Ruan is dead & simultaneously find out that Sarah is dead. They trace down Warns's family, hold them hostage & force Warns to call Thomas & make him come down to the docks. Thomas meets Danielle & appraises her of the situation. Apparently Danielle is running this whole show.

Thomas arrives at the docks & is shot at by Jacob. He confesses that Danielle & Warns worked for a military contractor, who wanted to see Thomas elected Mayor. As Mayor Thomas had promised more firearms for the police, which would come from the contractor. To discredit his opponent, Thomas had Warns bring in an illegal cache of firearms to sell to kids, who would later be arrested, which would lead to another big gun control scandal for the incumbents. But when Otis & Ruan showed up at the docks to buy guns, Otis recognized Harvey as the cop who arrested him an year ago. So Harvey shot Otis, but Ruan escaped with money & a gunshot wound.

The military contractor sends in its soldiers, who are shot down by Jacob & Max fighting together. Max shoots Warns & Jacob kills Thomas. Max allows Jacob to walk away.