On an island off the coast of California, Dr. Phillip Stevens holds weekend encounter sessions offering clients exercises to learn to relax, communicate and free the mind and body. Before the session officially begins, one participant, Cathy, is harpooned to death by an unseen attacker in the island’s forest. Carrying on, Phil opens the session with an icebreaker in which participants walk around the room touching one another. Sitting in a circle, the group members introduce themselves and explain what they hope to accomplish. As Phil notes, there are many reasons why people sign up. For example, he says, many people come “to get their heads together” or to acquire a sense of liberated living. Denise, a vacuous actress, believes that the session will improve her performance skills. Allison, a nurse escaping her overly possessive boyfriend Bud, says she wants to meet new people. George, a shy, stammering bumbler, says he just wants to “get laid.” In the next exercise, which has been designed to allow participants to lose their personal identities and merge with that of the group, the lights are turned off and individuals again mill around, pressing against each other, and are encouraged to remove their clothing. As Phil urges each participant to take in the “essence” of the others, a scream pierces the dark and when the lights are raised, it is revealed that someone maliciously injured Denise’s breast. While she is given first aid, Phil promises to check everyone’s reference files to determine who is likely to have hurt her. Lola, a college sophomore, wants her first sexual encounter to be enacted exactly according to her fantasy. When she decides that she would like to lose her virginity with Blue, a gentle rodeo bulldogger from Texas, Allison warns her not to take risks until the culprit has been identified, but Lola trusts Blue, who agrees to her request. Lola then explains the details of her fantasy, which is to be walking alone in a white dress on a beautiful night, and be captured, bound and forced to have sex. Unexpectedly, Bud joins the group, saying that he learned of Allison’s plans and followed her. He jealously warns Allison that she cannot get away from him, and when he becomes loud and abusive, Blue and Morris, an African-American businessman attending the session, come to Allison’s defense. The next scheduled event features a belly dancer, who encourages the group to dance. As several partners form, George makes a crude overture to Allison, but she is insulted and refuses. Shannon, a flirtatious nymphomaniac who tries to lure men away from the other women, cuts in and dances with George, urging him to touch feel her breasts and kiss her, then leaves abruptly to flirt with other men, including Bud, who is still too preoccupied with Allison to be attracted to Shannon. Trying to avoid Bud, Allison eventually dances with George, who makes her promise that she will talk with him later. Andrew, a forty-nine-year-old, never-married engineer, approaches Phyllis, who introduced herself earlier as a fashion designer. Having little experience with women, Andrew awkwardly spills a drink on her dress. Although she is angry at first, Phyllis invites him to the room she shares with Allison, Shannon and Lola. By the time Andrew arrives, Phyllis has changed to a clean dress but gotten the zipper stuck and asks for his help. As they struggle to unjam the zipper, an unnoticed observer watches them through the window. Lacking finesse, Andrew tells Phyllis that he wants sex, but she says she is a “nice Jewish girl” and will only provide it if she is married. He promises to marry her Monday, but the arrival of some of the other women interrupts their negotiations. After spending time in the moonlight with Blue, Lola returns to the suite and tells Allison she plans to carry out her fantasy the next evening. Outside, someone observes and listens. The next day, Bud apologizes to Allison, and she forgives him, but insists that he accept that she no longer cares for him. Their discussion continues as they explore a cave and she explains that his obsessive jealousy forced her to leave him. Later, when Allison is sunbathing alone, George sneaks up and reminds her of her promise to spend time with him. Although at first unnerved by his sudden appearance, Allison suggests that he try being less pushy if he wants to attract women. Also apologizing for his behavior is Andrew, who tells Phyllis he drank too much the night before. Warming to him, she confesses that she is a low-paid window dresser and not a fashion designer, but he says he is financially secure and does not care. Seeing their romance blossoming, Shannon lures Andrew to her. However, during the next sensitivity exercise, called the “blind walk,” Phyllis and Andrew reunite and Andrew leads the blind-folded Phyllis away from the group, unaware that they are being watched. Seeing George and Allison choose each other as partners, Bud becomes jealous and attacks George, who effortlessly knocks him out. Meanwhile, Andrew leads Phyllis to a greenhouse to make love, but the mysterious observer strikes Andrew on the head then stabs Phyllis several times with a pitchfork. Later, the embarrassed and remorseful Bud promises Allison that he will behave, and they agree to attend a dance that evening together. Bud accompanies Allison to her room, where she discovers that someone has gone through the women’s belongings and cut up their clothes. Although Blue arrives to pick up Lola, she says that her fantasy requires that they encounter each other at the appointed place rather than go there together. Later, when Lola is walking along the beach, Blue carries out her wishes, but as he starts to make love to her, someone strikes him from behind then kills Lola. The next morning, Allison expresses concern that Lola and Phyllis are missing, but Shannon jokes that it leaves more men for her. Allison then asks Shannon to accompany her to the cave area where Lola had planned to meet Blue. George sees them sail away, then turns his attention to Morris and Denise, who discover Andrew’s body. Revealing that he is not shy and bumbling, but an undercover agent tracking a serial killer, George sends Morris to alert Phil then follows Allison and Shannon. When Allison finds Lola’s body in the cave, Shannon confesses that she killed her, as well as Phyllis and many others. She explains that the women came between her and all the men who love her, and that she must kill Allison to free Bud for herself. Allison manages to run out of the cave, but Shannon overtakes her and throws her to the ground. Just as Shannon is about to stab Allison, George arrives and calls out her name. Later, after apprehending Shannon, George walks with Allison along the beach and admits that he likes—even loves—her.