Construction worker Mike is thrust into the world of espionage when his high school sweetheart, Roxanne, recruits him for a high-stakes intelligence mission.
Mike McKenna (Mark Wahlberg) is a construction worker from New Jersey whose life changes unexpectedly when his high school sweetheart Roxanne Hall (Halle Berry) re-enters his life after 25 years. She is now a secret agent for a covert organization known as "The Union" and recruits him, initially against his will.Mike was dating Nicole (Dana Delany) his 7th grade English teacher. Mike lives with his mother Lorraine (Lorraine Bracco). His friend Ronnie is getting married and Mike is the best man who is supposed to plan the bachelor party for the gang including Bobby (Patch Darragh) and Johnny (James McMenamin).
Tranquilized by Rox, Mike wakes hours later in London. Rox explains how she got him there, and he hurries out of the luxurious hotel and meets her boss Tom Brennan (J. K. Simmons). They brief him on a high-stakes mission, claiming his unassuming identity is the perfect cover. Tom says that unlike CIA or the FBI, The Union values street smarts over book smarts. They recruit normal working people, who can get the job done.
The Union is in turmoil after a botched operation in Trieste, which led to several agents' deaths. The mission was to extract a CIA rogue asset Derek Mitchell who had the list of all of US undercover agents and their identities on a hard drive, inside a briefcase. Roxanne watched from afar as Nick Faraday was the last agent to be shot, along with the asset and the briefcase take away by people inside a van.In desperate need of a fresh face, they turn to Mike, a "nobody," for a critical mission to retrieve government intelligence about law enforcement agents in various agencies.
The briefcase containing the sensitive information on individuals who have served allied Western nations is being auctioned off to the highest bidder. Juliet Quinn is the auctioneer who is selling the intelligence on the black market in London, on behalf of a mystery seller. The auction is in 2 weeks.The perilous operation spans across Europe and includes a series of international threats, including Iranian terrorists, North Korean agents, and Russian spies. The other members of the team are Athena (Alice Lee), Frank Pfeiffer (Adewale Akinnuoye-Agbaje), Foreman (Jackie Earle Haley).
Mike goes through vigorous training, normally done over six months but condensed to under two weeks. He is given another identity, undergoes psychological tests, is trained in hand-to-hand combat and sharpshooting, all while trying to keep up with the highly skilled Roxanne.
Sent by The Union with five million to buy an opportunity to bid at the intel auction. Mike has to go deliver the cash and pick up a device that allows the buyer to bid remotely. The exchange goes smoothly, but then Mike is immediately ambushed by who they believe is another interested party. The team barely gets him out in time, but the auction access device gets irreparably damaged. The arms recovered indicated that the attackers were Russians. Foreman believes that the Union has a leak as 2 of their back-to-back missions were compromised.The other groups in the auction include China, North Korea, Syria, Russia and Iran.Out of money, The Union decides to also fight dirty, tracking down the Koreans' mercenaries in hopes of acquiring theirs. The auction is in less than 48 hours.
The Union successfully infiltrates the Koreans, grabbing their device. However, the Union's communications expert Athena is found out and killed in the van. The team watches from a distance in horror as their headquarters (BT Tower) is damaged. Forced to go into hiding, the next evening the team regroups for the auction. Tom bids with CIA money, while Foreman works on tracing Quinn's (Jessica De Gouw) location and Rox and Mike speed to reach her. Tom keeps bidding to give Foreman enough time to trace Quinn's location.
Juliet Quinn is forced by Rox and Mike to take them to the briefcase. At her place, just before they are to leave with it, Nick Faraday (Mike Colter) arrives at the door. Warning that they are all in grave danger, he convinces Rox to let him in. It is revealed that Nick is one of the six Union agents believed to have died in Trieste. He claims Tom Brennan, the founder of The Union, is the mole, then Mike discovers that Nick was Rox's husband.
Convinced to meet with a CIA liaison Cameron Foster (Stephen Campbell Moore) at a bridge the next day, Rox and Mike leave together with the briefcase. In the car, he is upset she had not mentioned Nick, and she insists they had been separated. Made to feel he has lived a small life, Mike announces he is done, getting out of the car.
However, Mike cools off and shows up at the bridge drop off in the morning where they both apologize. Nick calls Rox, revealing he has framed her and Brennan by transferring money into Brennan's account, as he's planning to sell the intel to the Iranians. He got Quinn to switch briefcases at the apartment when Rox and Mike were focused on him.Nick got tired of never getting credit nor decent reimbursement for work at The Union. Mike and Rox escape as the CIA closes in.
Tracking Nick to Istria, Rox and Mike interrupt the deal with the Iranians, who pull out. Rox finds that Nick was cheating on her with Quinn.Then Juliet also pulls out with her men. Mike suddenly appears on a motorbike and Rox tosses him the briefcase. After a chase around the town by the Iranians, they finally are back together, when Nick and Mike have a standoff. To not risk Rox's life, Mike puts down his gun, but Nick is distracted by the Iranians, allowing Mike and Rox to escape. Mike loses the briefcase and Nick picks it up.During a subsequent car chase, Rox pauses when she believes he died when Mike's car skids off the mountain road into a ravine below. But Mike survives and joins Rox in her car. Finally, they catch up to Nick on the dock, who chooses to die rather than let Rox take him to jail.
On Sunday, at Ronnie's wedding, Rox shows up. They call each other out for showing they cared about each other. As they are about to sneak off together, Brennan appears and invites Mike to join them for an upcoming mission.