Tattoo artist Karl Kinsky is approached to work with renowned photographer Halsey on temporary tattoos for swimsuit models. Despite his misgivings, Kinsky agrees to participate after seeing photographs of one of the models, Maddy.
Maddy arrives late to the photoshoot, but the two quickly bond when she expresses admiration for Kinsky's arm tattoos and recognizes their Japanese influence. After the shoot, Kinsky jealously eavesdrops on Maddy and her flirtatious boyfriend, jazz musician Buddy. Maddy complains of having had to “dope” herself to sleep because of Buddy's odd hours. Maddy invites Kinsky to dinner, where he awkwardly asserts his dominance towards the maître d', and then threatens to kill Maddy's ex-boyfriend Albert for using profanity and drunkenly flirting with Maddy. They quickly leave the restaurant and drive to Maddy's apartment. She invites him in, but he declines, saying he has to catch the last train home. Instead, he goes to a sex show and aggressively speaks to a peep show girl.
The next day, Kinsky surprises Maddy in Central Park with flowers. After confronting her over her use of sleeping pills, he invites her to dine with him at his apartment. She admires his tattoo equipment and artwork. Kinsky explains his theory that women who get tattoos, which he calls “the mark”, do so out of a desire to belong. The two go upstairs to dine, and listen to Buddy's music. Kinsky tells Maddy she deserves better than Buddy, citing his handsiness. Maddy calls him "old-fashioned," but begins to make a pass at him. Kinsky turns her down, citing a need for commitment. Maddy tells him, "People don't make commitments when they fuck anymore" and Kinsky snaps at her over her use of profanity. He kicks her out but follows her to the street, insisting that they see each other again. She agrees to meet him at a Japanese art exhibition at the Met before speeding off in a taxi. The same night, Kinsky repeatedly telephones and berates Maddy from a telephone booth. When she asks him to stop, he returns to his apartment and intently watches her modeling tape.
On the day of the exhibition, Maddy sends her friend Sandra to tell Kinsky that Maddy is out of town, and to ask him to return her modeling tapes. He visits Maddy's apartment, where he is told the same thing by Buddy. He leaves an ominous message on her answering machine, before returning to his family's home to show it to prospective buyers, only to announce that it is not for sale.
Back in Maddy's apartment, she kicks Buddy and his jazz band out for keeping her awake. As she is cleaning up, the doorbell rings. When she answers the door, Kinsky incapacitates her with a chloroform-soaked rag. The next morning she awakens and discovers her chest, shoulders and back have been tattooed with floral patterns. She screams at Kinsky and smashes a mirror once she realizes she has become a hostage. Once Kinsky tells her he is not finished tattooing her, she faints. The next day, the tattoos have been partially colored in. Maddy makes a failed escape attempt, after which Kinsky has her call Buddy at knifepoint to tell him she will not be coming home. Recognizing Kinsky's increasing violence, Maddy agrees to “wear the mark” in exchange for her safety.
Nearly finished with the tattoo, Kinsky stops and has Maddy masturbate while he watches from another room, much like the peep show he visited earlier. Kinsky orgasms just as she begins weeping. Maddy berates him for not "being a man" and having sexual intercourse with her instead. She finds a shard of glass from the mirror and plans to kill Kinsky with it, but is discovered. She seemingly resigns herself to her fate as Kinsky continues to expand the tattoos over her entire body.
Maddy is shocked when Kinsky finally announces, "It's all finished." He disrobes them both and begins to rape her. Maddy is able to grasp the tattoo gun and plunges it into Kinsky's back. As Kinsky dies, Maddy sits up, his limp body draped across her lap. She strokes his hair as she stares off into the distance.
