Set in a mysterious, color-coded, anonymous city, a young woman meets a mysterious employer in a confession booth at a local church and implores him to employ her as his sole contract killer. To prove her worth, she offers to eliminate his other contractors. In exchange for her efforts, she asks if he can find someone for her.Meanwhile, Bill (Simon Pegg) is standing on a deserted train platform and is told by a limping janitor that no trains will be coming until 4:04 in the morning. The janitor suggests he wait in the 24-hour Cafe. There, he converses with Annie (Margot Robbie), a waitress, who notices that he has a terminal disease, and is suicidal. She discusses various ways he can kill himself.Three weeks earlier.Illing (Nick Moran), a hit-man, is captured by Annie, who is posing as a prostitute. He awakes to find himself handcuffed to a bed before Annie incapacitates and kills him.Mr. Franklyn (Mike Myers), the employer, calls his two hit-men - Vince and Alfred - (Dexter Fletcher and Max Irons) and orders them to pick up a briefcase from the lockers at the train terminal. They take it to the cafe and find a pack of matches and an envelope of money. They wonder why Mr. Franklyn has called on them, and not Illing. The match pack is from a strip joint, where they find a dancer resembling the waitress Annie from earlier. She takes the envelope of money as payment for passing on information about the hit Mr. Franklyn wants them to do. She comes on strong to Alfred but is dismissive of Vince. The hit-men are told to wait in an apartment and to shoot a person in the window opposite when told. Vince is also secretly told via a phone call to then kill Alfred. The waitress tells Alfred that Vince will try to kill him, so Alfred should kill Vince once the hit is completed. Mr. Franklyn watches from his lair, with monitors displaying camera footage of the cafe and the hit-men's hideout.Back at the train terminal, Annie the waitress takes Bill to an abandoned air shaft and tries to talk him into committing suicide. Although he described throwing himself down a deep, dark hole as his final act, he cannot jump. Annie teases him, and Bill tells the waitress that she is a "naughty girl". This triggers a memory from his days as a school teacher, where he had two girls in his class that he abused. The waitress reveals that she is one of those girls, and then she stabs Bill in the neck with his pen and pushes him down the shaft.Meanwhile, Mr. Franklyn calls the hit-men's apartment and says that they should be ready to take the shot. Vince trains his sniper's rifle at the window across the courtyard but is surprised to find Annie in his cross-hairs. Alfred pulls his gun on Vince and disarms him. Annie comes over and Alfred shoots Vince. Alfred and Annie leave the apartment and run into the janitor, who is arriving to clean up the murder scene.Back in the terminal, the waitress turns on Alfred, tells him that she is not infatuated with him, and shoots him dead. The janitor comes along to clean up the body. The waitress decides to help the janitor take the bodies to the top of the air shaft and drop them both into it. The janitor returns to the terminal and enters the janitor's closet, which is actually Mr. Franklyn's control center. He is revealed to be Mr. Franklyn in disguise, removing his prosthetic bad teeth and fake latex skin. He stops limping and walks normally. There are dozens of attaché cases lined up for future jobs. As he leaves his "closet", he is accosted by the waitress and her doppelgänger, revealed to be a set of twins, Annie and Bonnie.The twins tie up Mr. Franklyn and describe how their mother died. She was being pursued by her partner, revealed to be Mr. Franklyn - a.k.a. Clinton Sharp - after she witnessed him murder someone and ran back to her flat to protect her twin girls. Mr. Franklyn poured gasoline in her home, and set it on fire. The mother had time to push the girls out a broken window, but could not save herself. After that, the twins spent the rest of their childhood in an orphanage being molested by Bill. The twins tell Mr. Franklyn that he is their biological father and they are ready to exact their revenge. Despite Mr. Franklyn's pleas for mercy, the twins lobotomize him, finally kill him, then walk out of the terminal together.