Since faking his own death, Arthur Bishop has been living quietly in Rio de Janeiro under the name Santos. He is approached by a courier, Renee Tran, who knows his true identity and explains that her employer wishes Bishop to kill three targets and stage their deaths as accidents. Bishop escapes, eluding her and her mercenaries and fleeing to Thailand. He takes shelter at the resort island beach house of his friend, Mei, and learns that Tran is working for Riah Crain.
Some time later, a bruised woman, Gina Thornton, approaches Mei for first aid before returning to a boat anchored nearby. Mei sees her being beaten by a man aboard the boat and alerts Bishop. Together, they rescue Thornton, but in the scuffle, the man’s head hits a bollard and he dies. Bishop searches, unsuccessfully, for evidence of the man’s identity, then sets the boat ablaze.
While Mei tends to Thornton’s injuries, Bishop finds that Thornton is also connected to Crain, and concludes that he anticipated Bishop would become romantically involved with her: he would then kidnap her to make Bishop take the assassination jobs. On being confronted with his theory, Thornton reveals that Crain had threatened the children’s shelter in Cambodia that she runs unless she participated. Over the next few days, Bishop gets to know Thornton better and they fall in love. As expected, Crain’s mercenaries arrive and abduct them.
Crain keeps Thornton hostage to ensure Bishop completes the assassinations. The first target is a warlord named Krill, held in a Malaysian prison. Bishop gets himself imprisoned, and gains Krill’s trust by killing a man who attempts to kill him, Krill’s former right-hand man. Bishop then kills Krill himself by overdosing him with snake venom and escapes with the help of Crain’s operatives.
The next target is Adrian Cook, a Sydney-based billionaire and former trafficker of underage sex workers. Bishop bypasses Cook’s penthouse apartment’s tight security, breaks the glass bottom of his overhanging pool with a tube containing chemicals, causing the glass to crack and sending him plummeting to his death.
While relaying details of the third target, Crain allows Bishop to speak to Thornton, who repositions the camera, enabling Bishop to identify Crain’s boat. Bishop attempts a rescue, but Crain is able to thwart it.
The final target is Max Adams, an American arms dealer in Varna, Bulgaria. While planning his attempt, Bishop realizes the targets are Crain’s major arms dealing competition. He approaches Adams to warn him of Crain’s plan and recruit his help. Faking Adams’ death, Bishop reports his success to Crain, directing him to the submarine pen to find the body.
At the pen, Bishop decimates Crain’s mercenaries then makes for Crain’s boat anchored nearby. He fights off more of Crain’s men and rescues Thornton. Discovering the boat is rigged with explosives, Bishop puts Thornton in an emergency release pod. He kills the remaining mercenaries, then overpowers Crain and secures him to the boat with a metal chain. The bombs explode, killing Crain and seemingly Bishop.
Thornton is rescued and the remains of Crain’s boat are salvaged. Thornton returns to Cambodia and her teaching duties and is surprised when Bishop turns up. Adams discovers Bishop survived by escaping in a watertight anchor chain locker, but destroys the evidence as a token of gratitude for sparing his life and enabling him to monopolize the arms trade.
