Chance Miller is at home dreaming that he is shaving in his bathroom. When he looks in the mirror, he realizes that his reflection is gone and his hands are covered in blood. He wakes up in bed next to his girlfriend, Jackie, who asks if everything is fine. Chance reassures her and goes to the bathroom, the same one as in his dream. When Jackie prepares to go to work, she warns Chance that they're three months behind on rent and their landlord wants the rent. Chance says that he has a deal set with a bookie, Ronnie, and that he'll have the rent in 24 hours. Jackie isn't convinced and points out that Chance was supposed to have a sales job, but Chance says that the deal with Ronnie is a sure thing. She kisses him and says that she wants him and then leaves for her waitress job.
Once Jackie is gone, Chance takes a vase and goes to Markham Antiquities. The place is closed for the holiday weekend, but Chance calls the owner, Walter, and reminds him that he agreed to see him there at 5. Walter is reluctant to let Chance in until Chance says that he has the vase Ray Hoffman owned. The owner buzzes Chance in and escorts him to his back office. Chance notices an antique mirror which Walter dismisses as nothing special, and then examines the vase. While he waits, Chance stares at the mirror and is surprised to see his reflection waver and change for a moment.
Once he's done examining the vase, Walter offers Chance $5,000, explaining that it's not the one he thought when he saw it at the party and offered Chance $45,000. Chance insists that he paid a lot more for it, covering up Walter's involvement as the owner requested. Walter offers to talk to Hoffman but Chance checks Hoffman's number and discovers that it has been disconnected. The owner plans to leave for the holiday weekend with his wife and tells Chance to come back the next Tuesday to get the $5,000. Chance begs him for the $45,000 he promises, but Walter says that they didn't have a deal, just a discussion. He realizes that Chance spent everything he had to buy the vase, and Chance admits that he spent $20,000 based on what Walter told him.
Walter lights up a cigarette and insists that he was mistaken about the vase, but Chance accuses him of working with Hoffman to con him out of $20,000. He knows from rumors that Walter keeps cash in his office, enough to cover his payment, and tells Walter to get it out. Walter tells him to take the $5,000 and orders him out, but Chance goes berserk and attacks Walter. He chokes the owner and after a brief fight, Walter trips on the mirror and hits his head on a table, apparently dying. Shocked, Chance starts to leave but hears something out in the shop. He grabs a cane and goes to check it out, and finds... himself.
Second Chance tells Chance that he's pathetic and walks away. When Chance goes back to get the money, he discovers that Walter is still alive. The owner tries to get to the phone and the desperate Chance beats him to death with the cane. Second Chance comes in and asks if Chance plans to kill him as well. When Chance claims that Walter's death was an accident, Second Chance points out that it doesn't look like that and congratulates Chance for giving Walter what he deserved. He offers to help but Chance refuses so his counterpart walks out.
Chance goes to Walter's adjoining bathroom and treats the cuts that the owner gave him in the fight. He starts to take the $5,000 from Walter's pocket, but the lit cigarette sets off the smoke alarm. Chance panics and tries to turn it off, and finally breaks it with the cane. The phone rings and Chance has no choice but to answer it. It's the security company, and Chance tries to bluff it out. He doesn't know the password and the man at the other end hangs up.
Chance cleans up the office and starts to go, but a security guard arrives. The guard, Geaghan, knocks on the door and Chance opens the door rather than let the man call in the alarm. Chance claims that he's Walter's assistant and that the owner left for the weekend and didn't give him a password. Geaghan asks to see the detector and Chance takes him to the back office. They go back while Second Chance watches from the shadows. Chance almost manages to bluff Geaghan, but the guard spots Walter's corpse and Chance stabs him to death with a sword.
As Chance tries to get over the shock, he hears his counterpart going up the stairs. He follows Second Chance up and finds the image pouring two drinks. Second Chance congratulates Chance on the murder, noting how brutal he was, but warns that he left fingerprints all over the place. Also, he points out that Walter said he was going on holiday with his wife and she'll undoubtedly be there in a few minutes. Chance goes back down and hides Geaghan's body, while Second Chance says that Chance called Walter and the police can trace the call. Working together, the two Chances take the bodies out to the dumpster and then clean up the blood. As they pick up, Chance realizes that Walter severed two of his fingers on broken glass and pockets them.
Jackie calls Chance and asks why he's running late. He tells her that he has the money from Ronnie and she suggests that they take a trip to celebrate. Chance hangs up and Second Chance wonders what he plans to tell his girlfriend. Before he can come up with something, Walter's wife comes into the shop. She goes upstairs and Second Chance tells Chance that they need time to find the rest of Walter's money. The wife will come down eventually so Second Chance tells Chance to kill her. Chance realizes that if he doesn't go back with the $45,000, Jackie will never forgive him. Second Chance assures him that he's the only one who cares about him, and tells Chance to find the $45,000 and get his life back on track. Shocked, Chance insists that he can't kill like his counterpart, and Second Chance tells him that's his problem.
The wife is surprised to find a single empty glass on the bar. She takes a shower and Second Chance prepares to kill her. Chance refuses but discovers that his counterpart isn't listening. He goes downstairs as the wife emerges from the shower, and she sees Second Chance in the mirror. He strangles her while in the alley below, Chance hears her scream and runs.
Back at his apartment, Chance discovers that Jackie went to the store to get something to celebrate with. He pours himself a drink and waits, and Jackie finally arrives. She calls out to tell Chance that she has a surprise, and Chance looks in the mirror. He's surprised to discover that his cuts have gone and that he now remembers successfully getting the $45,000 from Walter and that no one died. However, he's simply imagining things. Jackie comes in with champagne and sees her boyfriend holding Walter's severed fingers and covered in blood. The memories of what really happened flood back in, and Second Chance smashes in the door. He grabs Jackie and closes the bedroom door separating himself from Chance. Chance collapses, begging Second Chance to stop, but Jackie's screams fill the apartment.
The police are called in and find Jackie's corpse. One officer finds Walter's fingers on the floor and Chance cowering behind the bed. When the cop orders Chance to surrender, he raises his blood-covered hands in surrender. The police take him out to their car while the neighbors watch and wonder how such a nice man can become a murderer. In the back of the squad car, Chance looks at his own reflection in the rear-view mirror and smiles.