Yuichi Kimura, “The Father”, boards a bullet train in Tokyo in search of the attacker of his son Wataru. Meanwhile, guided by his handler Maria Beetle, operative “Ladybug” is assigned to retrieve a briefcase full of cash from the same train, replacing a sick colleague, Carver. Ladybug is reluctant, as his recent string of bad luck during his jobs resulted in accidental deaths. Also on the train are two British assassin brothers codenamed “Lemon” and “Tangerine”, who just rescued a man (“The Son”) from kidnappers and are taking him and the briefcase to his father, a Russian-born Yakuza crime lord called “The White Death”.

During the trip, The Son is killed by poisoning. Ladybug discreetly steals the briefcase, but on his way off the train, is attacked by another assassin, codenamed “The Wolf”, who recognizes Ladybug from his wedding, where his wife was killed. The Wolf mistakenly believes Ladybug to be one of her killers. Ladybug confusedly fights The Wolf, who accidentally kills himself with a deflected knife throw. Yuichi finds the person who pushed Wataru, a young woman codenamed “The Prince”, but she outsmarts him. She lured Yuichi to the train as part of a plan to have him kill his boss: the White Death. To ensure his cooperation, she has a henchman holding Wataru hostage in the hospital.

Recognizing Lemon from a job in Johannesburg gone wrong, Ladybug offers to return the case in exchange for being allowed to leave. Lemon suspects that Ladybug killed The Son, leading to a fight. Lemon is knocked unconscious during the fight and Ladybug spikes his water with sleeping powder. Tangerine wakes Lemon up and they both split off to find Ladybug and frame him for the Son’s murder. The Prince finds the briefcase, booby-traps it with explosives, and rigs Yuichi’s gun to explode if fired. Ladybug encounters Tangerine and, after avoiding the White Death’s men, kicks Tangerine off the train as the train departs, but Tangerine manages to climb back aboard from outside.

Suspicious of the two, Lemon shoots Yuichi and is about to shoot the Prince, but collapses after drinking from his water, which Ladybug had previously spiked with sleeping powder. The Prince shoots Lemon and conceals him and Yuichi in a bathroom. Ladybug encounters another assassin, codenamed “The Hornet”, who poisoned both the Wolf’s wedding party and the Son with boomslang snake venom. After a struggle, both are exposed to the venom, but Ladybug takes Hornet’s antivenom before she can, killing her. Tangerine runs into the Prince and notices one of Lemon’s train stickers on her, realizing that she shot Lemon. Ladybug interrupts them, and Tangerine is killed before he can shoot the Prince. At the next stop, Yuichi’s father, “The Elder”, boards the train. He recognizes the Prince’s voice and informs her that Wataru is safe as her henchman has been killed.

After she flees, the Elder tells Ladybug he will remain to confront the White Death, who killed his wife while taking over the Yakuza. Finding Yuichi and Lemon still alive, the four work together and prepare to face the White Death. At Kyoto, Ladybug gives the White Death the briefcase. The Prince, revealed to be the White Death’s daughter, fails to goad him into shooting her with the rigged gun. The White Death explains that everyone on the train was linked to the death of his wife. He hired them hoping they would kill each other, not knowing Carver (his wife’s killer) was replaced by Ladybug. The White Death’s henchmen open the briefcase, which explodes, knocking Ladybug and the White Death back onto the train.

The White Death’s remaining henchmen board and battle the assassins, while the Elder duels the White Death. The train crashes into downtown Kyoto. Emerging from the wreck, impaled with the Elder’s katana, the White Death tries to kill Ladybug, but the Prince’s rigged gun explodes in his face. The Prince threatens Ladybug, Yuichi, and the Elder with a machine gun but is run over by a truck full of tangerines driven by Lemon.[6] Maria arrives to retrieve Ladybug, while Japanese authorities begin to clean up the damage caused by the train crash.