A dead man is seen being pulled by his feet by someone off-camera, and his voice says that the culprits for his state are the praying mantis ("les garces", in French dialogue). The story unfolds, in flash-back.Eliane is a 30 year old fake blonde, living in a small suburban house, which she shares with her sweet friend Juliette. They are intimate, sharing the house, but sleeping in separate rooms. After a good-night kiss, Eliane goes to her room, and before she goes to sleep, she hears a police warning on the radio about a serious criminal, Pierre Richards, who escaped while being transferred from one prison to another, as he was serving a long sentence.Next morning, driving alone, she slows down near a bend and a wounded man jumps into her car from a road-side ditch. With a dagger at her throat, he asks her to take care of him, and she drives off. He passes out in the passenger seat, and she takes him home. Eliane treats the man, and hides him in her attic, keeping it a secret from Juliette.The wounded man recovers, reveals himself as Pierre Richards, and becomes Eliane's lover; the power of his attractions becomes an obsession with Eliane.Pierre, from his comfortable but secluded life in the attic, overhears Juliette having a sex romp with her regular visitor, Gérard, during Eliane's absence. Pierre keeps his hiding, but watches their sex session - and he starts lusting for Juliette.One day, menacing Eliane with his flick-blade, he forces Juliette to strip naked for him. Eliane leaves, he strips too, and finally has sex with the younger brunette.Another day, again with the menacing knife, Pierre forces Eliane to hear Juliette having sex with Gérard, while he fondles Eliane's breasts under her sweater, and Eliane suffers Juliette's betrayal standing outside the bedroom door.Eventually Juliette, pressured by Eliane, decides to break away with Gérard, and after having sex one more time, she tells him not to return. However, when she goes to tell the news to Eliane - wearing a black negligee over her nude body - she is surprised to see that Eliane is having sex with Pierre! She interrupts them, and Eliane jumps out of bed, tells that Juliette is too naive, and slaps her. The two estranged lovers fight, and roll on the floor, under Pierre's voyeuristic gaze.Pierre finally separates them, and takes Juliette to her own room, where the girls enjoys the touches of this mature man.Taking advantage of the women's quarrel, Pierre becomes the master of the place, submitting the two women in turn to his desires. Eliane and Juliette get together again, and this time they strip and make love together, for Pierre to see. They end up living in a threesome.A police inspector and his deputy are visiting all houses in the neighborhood, and knock at their door to know if the ladies have seen something suspicious about the fugitive Both declare they didn't, and the policemen leave.Then, Eliane is getting displeased with Pierre for showing more attraction to Juliette than to herself. Pierre starts a new game: the women in alternate mornings, take coffee and toasts to his bed - where he is still with the other. And he treats them badly.One day, he is mistreating Eliane when Juliette interferes. Eliane and Juliette have had enough. Eliane knocks him out, and both prepare his execution, and bury his corpse in the garden. After, they make love again while sharing a bath.Juliette hears Gerard sending pebbles to the window, and decides to invite him in again. Gerard and Juliette make love again, while Eliane caresses herself behind the bedroom door naked - until she can't stand it, and enters the room.