Snàporaz, Marcello Mastroianni, wakes up during a train ride and has a brief fling with a mysterious woman in the bathroom, but it is cut short when the train suddenly stops at Fregene and the woman gets off. Snàporaz follows her through a forest and into a hotel overrun with women attending a surrealistic feminist convention. He winds up in a conference about polyandry, where his presence is rejected. A frightened Snàporaz retreats to the hotel lobby, but the exit is blocked; instead, he seeks refuge inside an elevator with a young woman, Donatella Damiani, who offers her assistance.
Donatella leads Snàporaz into a gymnasium and forces him to don roller skates. He is cornered and berated by a group of angry women who circle around him on skates and practice testicle-kicking with a dummy. Dazed, Snàporaz makes his exit down a flight of stairs, falls and hurts himself, and ends up in the domain of a burly woman tending to the hotel’s furnace. The woman offers him a ride to the train station on her motorcycle, but stops by a farm and lures Snàporaz into a nursery, where she tries to rape him. They are interrupted by the woman's mother, who chastises her daughter. Snàporaz escapes and follows a lonely woman through the countryside. He joins her and her girlfriends in a car ride, driven toward the station, but the journey lasts well into the night, the women smoking marijuana and blasting Italo disco. A frustrated Snàporaz ditches the group only to be harassed by others.
He finally finds shelter at the mansion of Dr. Xavier Katzone, Ettore Manni, who shoots at his persecutors. Dr. Katzone promises to deliver Snàporaz to the train station in the morning and invites him to stay for a party. The house is a carnival of sexual imagery and phallic sculptures, while Katzone shows a wall of photos chronicling his conquests—the pictures light up and murmur arousing dialogue.
During the party, Snàporaz runs into his ex-wife Elena, Anna Prucnal, who has a drunken argument with him, and he also encounters Donatella again. The police, composed entirely of women dressed in Nazi-like uniforms, arrive and interrupt Katzone’s revelry, announcing the demolition of his house. They inform him that his beloved dog Italo has been shot, a grief that he must endure. Meanwhile, Snàporaz dances to a Fred Astaire song with Donatella and a friend of hers, but he fails to sleep with either partner, ending up in bed with his ex-wife instead.
Strange noises pull him into a dreamlike sequence: he crawls under the bed and slides down a magical toboggan that revisits his childhood crushes—a sitter, a nurse, and a prostitute—until he is somehow transported before a bizarre court that judges him for his masculinity. He is dismissed and set free, ascending into a towering boxing ring before a female crowd. At the top of the ring, he boards a hot-air balloon fashioned as Donatella. Donatella fires from below with a machine gun, puncturing the balloon and sending Snàporaz crashing down.
Snàporaz wakes up on the very same train, Elena across the way, suggesting the entire sequence was only a nightmare. He also notices his glasses are broken, mirroring his dream, just as the mysterious woman and Donatella reappear and sit beside him. Elena and the mysterious woman exchange knowing smiles as the train races into a tunnel.