Inside his room at the Discount Inn, Leonard Shelby wonders how long he has been there. At the motel’s front desk, he shows a Polaroid photograph to desk clerk Burt, just as the smiling Teddy arrives. Teddy and Leonard then walk to the motel garage, where another Polaroid identifies Leonard’s car, a Jaguar with a broken passenger-side window. After the pair arrive at a deserted building, Leonard goes inside and looks at other pictures in his pocket. He sees a Polaroid of Teddy inscribed with the words “Teddy--Don’t believe his lies--He is the one--Kill him.” When Teddy comes inside, Leonard grabs him, holds a gun to his face and orders him to ask for his wife’s forgiveness. Teddy protests that Leonard does not really know who he is and pleads with him to go to the basement, but Leonard kills him. In his motel room, Leonard sees the name “Sammy Jankis” tattoed on his hand, then writes a notation about Teddy on the back of his Polaroid. Leonard grabs a gun and leaves his room, then talks to Burt, explaining that an injury has left him with a condition that prevents him from making new memories. Leonard asks him to hold all of his calls, except for those from one person, and displays Teddy’s photo just as the smiling Teddy arrives. While Leonard washes his hands in a men’s room, he sees the tattoo about Sammy and notices another tattoo that reads “The Facts.” When he leaves the men’s room, a waiter hands him a large envelope marked “For Leonard from Natalie.” In his room, Leonard carefully places his Polaroids on a large, hand-written wall graph, then opens the envelope, which contains a photocopy of Teddy’s driver’s license, listing his name as “John Edward Garmmell.” Leonard looks at Teddy’s photograph, which reads only “Don’t believe his lies,” then telephones Teddy and asks him to come over. As Leonard changes his shirt, he sees dozens of words tattooed on his body, some of which correspond to information on Teddy’s license. He then adds “He is the one” to the Polaroid, but after seeing a tattoo on his chest which reads “John G. Raped and Murdered my wife,” when reflected in the mirror, adds “Kill him. Leonard arrives at the coffee shop and reads the notation about Natalie on her photograph. Natalie, whose face is bruised and cut, shows him the contents of the envelope and says she added the address of an abandoned place outside town. She then hands him the key to his motel room, remarking that he had left it at her place. Using the telephone in his room, Leonard talks about Sammy, whom he met on an insurance investigation that was his first real challenge. As Leonard enters his Jaguar, Teddy pops in front of the car. Over lunch, Teddy confirms to Leonard that he has already heard about Sammy and Leonard’s condition, and asks if Leonard has found John G. After warning that someone may be setting him up, the men discuss Leonard’s contention that facts, not memory are important. Teddy promises to help him get John G., then Leonard looks at a photo of The Discount Inn and notices that he does not have his room key. When Leonard arrives at the motel, Burt lets him into a room, then admits that he has rented him two rooms, knowing he would not remember. Leonard then looks at one of his notes and rushes to the coffee shop to meet Natalie. Talking on the telephone about Sammy, Leonard explains that, after a car accident, Sammy displayed symptoms of Anterograde memory-loss disorder, which interferes with the mind’s ability to make new memories: Leonard visits Sammy, who remembers everything before his accident, and can administer his diabetic wife’s insulin shots, yet cannot remember what happened a few minutes before. Leonard wakes up in Natalie’s bedroom, sleeping next to her. She promises to talk to a friend about getting John G.’s license number, saying that she is helping him because he helped her. As Leonard leaves her house, Teddy pops in front of the Jaguar. In the early evening, an agitated Leonard pounds on Natalie’s door and shows her a Polaroid of a badly beaten man called Dodd. He asks what she has gotten him into, and she says that he did it for her, because of what Dodd did to her face. When she takes Leonard’s shirt off and sees the reflected tattoo about John G., she says she has lost someone, too, Jimmy, who was killed by a man named Teddy. After they make love, Leonard slips out of bed and writes the note about Natalie on the back of her photograph. When Leonard wakes up after dreaming of screams and broken glass, he opens a closet and finds a man with his mouth taped shut, just as Teddy is pounding on his door. After checking his photo, Leonard lets him in and Teddy says that he called him to come over. Teddy asks if the man in the closet is John G., then Leonard pulls the tape off the man, who says his name is Dodd and that Leonard did this to him. Leonard finds Dodd’s picture among his Polaroids and reads the notation “Get Rid of Him--Ask Natalie.” Leonard does not see any of his wall notes and realizes that this is not his room, then finds a gun in the drawer. With Teddy’s help, Leonard escorts Dodd from the motel and lets him go. In the early evening, Leonard drives the Jaguar to Natalie’s house. Continuing his telephone conversation about Sammy, Leonard recalls that Mrs. Jankis was emotionally and financially drained by Sammy’s condition, and Leonard suggested, but did not state outright to her, that Sammy was faking. Leonard finds himself in a motel bathroom, next to a bottle of Scotch. While he showers, Dodd enters the bathroom, and they fight. After Dodd is knocked out, Leonard looks through his notes, then takes a Polaroid of Dodd, writes “Get Rid of Him--Ask Natalie” on the back and puts him in the closet. He finds Teddy’s picture and phone number, then asks him to come to the Mount Crest Inn. Now running through a trailer park, Leonard quickly realizes that a man, Dodd, is chasing him. He sees the Jaguar, gets in and speeds away. As he does, he finds a note with Dodd’s name and room number at the Mount Crest Inn, drives there, and waits in the bathroom, holding a bottle of Scotch as a weapon. At dawn, after finding himself near an oil refinery outside town, Leonard drives his Jaguar into town and is followed by an SUV. The driver, Dodd, draws a gun on him, then shoots out the Jaguar 's passenger window as Leonard runs away. At night, Leonard drives the Jaguar past the refinery, builds a fire and burns a teddy bear, hairbrush and a paperback book as he thinks about his wife. At dawn, he leaves. On the telephone, Leonard talks about his own discoveries and says that he hoped to find out more about “the drug angle.” He then looks through the police report about his wife’s death, saying that friends in the department had helped him, but wonders why so much is missing and why they never followed up on John G. Leonard awakens to the sound of a door slamming and calls out to his wife. Opening the bathroom door, he sees a blonde taking drugs and asks her to leave, then takes some things to his Jaguar. In the morning, Leonard arrives at the Discount Inn and takes its photograph. Inside his room, he puts his graph and photographs on the wall, then orders a prostitute from an escort service. When the blonde arrives he tells her to put the hairbursh and other things around the room, then, after they have sex, go into the bathroom and slam the door. As Leonard draws a tattoo on his arm, he continues to talk about Sammy, and recounts a time when Sammy’s distraught wife came to see him: After she begs for Leonard’s real opinion, he says he thinks Sammy is physically capable of making new memories. As Leonard gets into his car outside Natalie’s house, he is startled to find Teddy inside and does not recognize him. Teddy says that he is his buddy and knows about Sammy, then adds that Leonard is still in town because of Natalie. When Leonard pulls out Natalie’s picture, Teddy tells him she cannot be trusted and gives Leonard the name of a place to stay, the Discount Inn. Teddy also tells Leonard that Natalie works in a bar and takes orders for her drug-dealer boyfriend. Teddy insists that Leonard write “Do Not Trust Her” on Natalie’s photograph, then intimates that Leonard does not know who he really is. When Teddy leaves the car, Leonard finds his picture with the words “Don’t Believe his Lies” and decides to scratch out the notation not to trust Natalie from her picture. Inside Natalie’s house, Leonard is desperately searching for a pen when Natalie comes in, disheveled, with a black eye and bruises. She says that Dodd beat her because he did not believe that “this Teddy” took everything and has threatened to kill her if she does not have the drugs by tomorrow. Leonard then walks out to his car and finds Teddy inside. In Natalie’s house, Leonard looks through the police file as Natalie comes in and closes the curtains, saying that a man called Dodd wants to know what happened to Jimmy and his money. Natalie asks Leonard to call Dodd, saying she will pay, but Leonard protests that he does not kill people for money. She then lashes out at him about his condition and yells obscenities about his wife. Enraged, he starts to slap her, then she walks out, saying “I’ll see you soon.” A few minutes later, Natalie re-enters the house as Leonard is searching for a pen. In Natalie’s living room, she asks how long it will take to find the guy who killed his wife. He then relates what happened: Waking up and hearing the muffled cries of his wife, Leonard grabs his gun and goes to the door of the bathroom, where he finds a masked man raping his wife. He shoots the man, but is grabbed from behind, thrown against the mirror and knocked unconscious. As Natalie leaves the house, Leonard snaps her photograph. Moments later, she re-enters the house and draws the curtains, saying someone is coming. At Ferdie’s bar, Natalie serves Leonard a drink and says that a cop has told her about his condition. On the phone in his room, a nervous Leonard is talking to a policeman. In the Jaguar, Leonard looks at a coaster for Ferdie’s bar, then drives there. He asks Natalie for a beer and she tells him that her boyfriend, Jimmy Grantz, told her about him and said that a cop was looking for a man who cannot remember anything. At his motel, Leonard continues to talk to the policeman and relates that after his meeting with Sammy’s wife, she went home and tested Sammy by asking him to administer her insulin shot, then repeated the request until she fell into a fatal coma. Leonard drives to Emma’s Tattoo Parlor and has “Fact 6: the car license number” tattooed on his arm. Teddy comes in looking for him and later says that the police are after him so he needs a new identity and new clothes. Teddy says that he is the “snitch” of a bad cop who checked Leonard into the Discount Inn, and that the cop is looking for Jimmy, who is a drug dealer. After Teddy leaves, Leonard sees the message “Don’t believe his lies.” Finding the Ferdy’s coaster, Leonard drives to the bar, where Natalie knocks on the window saying “Hi Jimmy,” then apologizes and leaves. On the phone, Leonard tells the policeman that Jimmy deals drugs in the bar where his girl friend works. He agrees to meet the policeman in the lobby, then immediately packs up his chart and finds Teddy, whom he addresses as “Officer Gammell.” After Gammell says to call him Teddy, he becomes annoyed when Leonard takes his picture, but gives him his phone number. He also gives Leonard an address and, as Leonard drives off in a pickup truck, shouts “make him beg.” Leonard then drives to the deserted building and waits inside. After Jimmy Grantz drives up in a Jaguar, he enters the building, calling for Teddy. Leonard pulls a gun on him and orders him to take his nice clothes off. Jimmy offers him $200,000, but Leonard refuses, saying he only wants his life back. He strangles Jimmy, then takes his picture, changes into Jimmy’s suit and puts his notes in the pockets. He then drags Jimmy down to the basment, but Jimmy is not dead and whispers “Sammy.” Frightened, Leonard rushes upstairs, just as Teddy arrives. Leonard slugs Teddy, thinking he has been set up, but Teddy tells Leonard he lies to himself to be happy. Teddy then reveals that Leonard’s wife survived the assault but was anguished because she did not believe Leonard’s condition. Teddy adds that it was Leonard’s wife, not Sammy’s, who died from the insulin shots and that the real Sammy was just a faker whom Leonard exposed. Teddy continues that he helped Leonard find the real “John G.” over a year ago and that Leonard killed him, but did not remember and has since been reliving the case. Teddy then jokes that there are plenty of John G.s to be found, in fact, he is one. As they leave the building, Leonard throws Teddy’s keys into the bushes. He thinks to himself that he is not a killer, then looks at Teddy’s picture and on the back writes “Don’t believe his lies.” After writing down Teddy’s license plate number, Leonard wonders if he lies to himself to be happy, then drives off in the Jaguar, thinks of his wife and stops at Emma’s Tattoo Parlor.