Compulsive womanizer Dave Garver (Clint Eastwood), who is a disc jockey at jazz radio station KRML in Carmel, California, is taunted by his fellow deejay, Al Monte (James McEachin), when Dave receives yet another request from a female fan to play Erroll Garner's jazz classic "Misty" for her.After the poetry-loving Dave finishes his shift, he goes to his usual hangout, a bar called The Sardine Factory, run by his pal Murphy (Don Siegel). Seeing an attractive woman (Jessica Walter) sitting at the end of the bar, Dave and Murphy play a nonsensical board game to get her attention. Her curiosity piqued, the woman comes over and introduces herself as Evelyn Draper. Evelyn laughs when Dave reveals his ploy, and they go to her home, where she confesses that she came to the bar to meet him. Dave then recognizes her voice and realizes that she is the fan who calls him every night with the request "play 'Misty' for me." Although Dave warns Evelyn that he is "hung up" on another woman, she is unconcerned and spends the night with him, with the stipulation that they will not "complicate" each other's lives.The next day, Dave is working at home when Al drops by, but they are interrupted by the appearance of Evelyn, who is carrying groceries. Assuming that Dave had a date with Evelyn, Al leaves, although a nonplussed Dave admonishes her for arriving so unexpectedly. Evelyn is cheered when Dave mentions that she should call "next time," however, and he lets her stay the night.Later, while driving through Carmel, Dave learns that artist Tobie Williams (Donna Mills), his former girl friend who left town four months earlier, has returned. Dave insists on talking with Tobie, and she explains that she could no longer endure waiting for him every night, wondering if he was with another woman. Dave assures her that he has been attempting to change, and states that although her series of eccentric roommates at her isolated Carmel Highlands home irritated him, he wants to resume their relationship. Tobie agrees to consider his proposal but cautions him that she needs time.A little later, Dave is at The Sardine Factory having a drink when Evelyn calls looking for him. Dave signals Murphy to tell her that he is not there, but when Dave leaves, he finds Evelyn waiting in the parking lot having followed him and made the call from a nearby payphone. Again made uneasy by Evelyn's bizarre behavior, Dave refuses to take her out, although in a few days, she again shows up at his house without phoning first. Dave is forced to let her in when she takes off her coat, revealing that she is naked, and once inside, she seduces Dave again. As she leaves the next day, she invites him to her house for dinner, but he replies that he will call her. Dave then goes to work, where he makes a demonstration tape for Madge Brenner (Irene Hervey), an influential radio-station owner who is interested in hiring Dave for a prominent San Francisco job.A few days later, Evelyn calls Dave to chide him for forgetting their date, and an irritated Dave soon arrives, determined to tell her that their relationship is over. Dave becomes infuriated as Evelyn sobs that she loves him, then screams violently at him as he leaves. When Dave returns home, Evelyn calls, begging him to forgive her, but he hangs up on her. Later, Dave spends more time with Tobie, and the increasingly forgiving Tobie makes plans to go to a party with him the following evening.That night, however, an hysterical Evelyn arrives at Dave's, waking him because she believes that Tobie is with him. Surprised to find him alone, Evelyn calms down, but when Dave demands that she leave, Evelyn goes into the bathroom and slashes her wrists. Dave calls a friend, Dr. Frank Dewan (Jack Ging), to tend to Evelyn, who has not been seriously injured, and Frank reluctantly agrees not to notify the police. Evelyn overhears as Frank cautions Dave to keep her calm, and easily manipulates Dave to let her stay by making him feel guilty.The next evening, when Dave attempts to leave to see Tobie, Evelyn pretends to have a nightmare, and Dave is forced to stay with her, thereby standing up Tobie. In the morning, Dave's feisty maid, Birdie (Clarice Taylor), finds him asleep on the couch. Evelyn has taken Dave's car into town to buy groceries, and while she is out, she secretly has a copy of Dave's house key made.Meanwhile, Dave receives a call from Madge, who wants to have lunch with him and discuss the new job. When Evelyn returns to Dave's, he explains that he is on his way to a business luncheon. As Dave and Madge are eating, however, an irate Evelyn arrives and hurls insults at Madge. Dave drags her out of the restaurant into a waiting cab, but when he returns, he finds that Madge has departed.Dave then goes to Tobie's and confesses his situation to her. While Dave is gone, Birdie returns to his house and discovers that Evelyn has destroyed the furnishings and is in the process of cutting up Dave's clothes. Surprised by Birdie's appearance, Evelyn slashes her repeatedly with a knife. Dave arrives as Birdie is being taken away in an ambulance, and the police, led by Sgt. McCallum, are questioning Evelyn. McCallum is irritated by Dave's lack of knowledge about Evelyn, but assures him that she will receive psychiatric help.As time passes, Dave and Tobie reconcile, and months later, attend the Monterey Jazz Festival, where Tobie mentions that a new roommate, Annabel, will be moving in with her. That night, Evelyn calls Dave as he is working, and, explaining that she has been released from the sanatorium, tells him that she is in San Francisco, on her way to Hawaii. She asks him to play "Misty" for her, which he does, but later that night, he wakes up to hear the song playing in his bedroom. Dave moves just as Evelyn attempts to stab him with a butcher knife, and she escapes before he can catch her.Shaken, Dave calls McCallum, who reveals that Evelyn had been released pending further legal action. McCallum presses Dave to remember Evelyn's exact words when she called him, especially the line of a poem that she quoted. Dave then warns Tobie that Evelyn has returned, and the next night, although Dave would rather be guarding Tobie, McCallum instructs him to stay at work, so that the police can trace the call if Evelyn telephones him.In order to reassure Dave, McCallum drives to Tobie's house to check on her, and after he leaves, Dave remembers that the poem Evelyn quoted was Edgar Allan Poe's "Annabel Lee." Realizing that Evelyn must be Annabel, Tobie's new roommate, Dave puts on a pre-recorded tape of one of his old shows and rushes to her home. By the time Dave arrives, however, Evelyn has murdered McCallum by stabbing him with a pair of scissors and bound and gagged the terrified Tobie, and has cut off some of her hair with the scissors. As Dave attempts to free Tobie, Evelyn jumps out of the darkness and attacks him with a knife, slashing him repeatedly. Although wounded, Dave succeeds in fending her off before she disappears. Dave searches the house for Evelyn, and when she attacks him again, she stabs him several times in his arms and left leg until he finally manages to punch Evelyn in the face with such tremendous force that it knocks Evelyn back through the back glass door and over the balcony railing and over the cliff, sending her falling to her death in the ocean below. As the wounded and bloodied Dave frees Tobie and they stagger from the house together, the pre-recorded tape plays Dave's dedication of "Misty" to Evelyn one last time.