Possession

Mark returns to West Berlin from an espionage mission to find his wife Anna suddenly asking for a divorce. She insists it isn't because of someone else but refuses to explain. Devastated, Mark moves out and leaves their young son Bob in her care, but when he returns from a drunken bender he finds Bob neglected and alone, and senses something is badly wrong.

Mark hires a private detective to follow Anna. The detective discovers she is seeing Heinrich, a flamboyant New Age mystic who speaks in riddles. Mark and Anna's confrontations grow hysterical and violent — they scream, slap, and beat each other in front of Bob and in cafés. Anna disappears for long stretches and behaves erratically, including a notorious sequence in a U-Bahn tunnel where she convulses, leaks blood and white fluid, and seems to undergo an ecstatic, demonic breakdown.

The detective's pursuit leads to a dilapidated apartment Anna has secretly rented across the city. Inside he finds a grotesque tentacled creature she has been nurturing and sleeping with. Anna murders the detective to protect it. A second investigator follows; she kills him too. The corpses are left to rot in the flat as the creature slowly evolves toward a more human, male form.

Mark meets Bob's schoolteacher Helen, who looks exactly like Anna but with green eyes and a gentle, maternal warmth — Anna's mirror opposite. Mark begins a quiet relationship with her, drawn to an idealized version of his wife. His sanity erodes as he uncovers more of Anna's other life; he becomes complicit, helping hide bodies and lying to authorities, while trying to keep a semblance of normal family life with Helen and Bob.

Anna keeps visiting the secret flat, treating the creature as her true lover. The thing in the apartment grows progressively more humanoid, taking on Mark's own likeness — she is sculpting an idealized double of her husband through sex and violence. Heinrich discovers the creature, is attacked and mutilated, and eventually dies. More cover-ups follow as Mark's spy superiors and the West Berlin police close in.

In the climax Mark is wounded and on the run with Anna, pursued through stairwells near the Berlin Wall. They reach the derelict building, where the now fully formed Mark-doppelganger — dressed in black, eerily composed — appears beside Anna as her perfected lover. In a shootout on the staircase both Anna and the original Mark are mortally wounded. Anna collapses against a door, pressing into it as she dies; Mark bleeds out in a bathtub, glimpsing his double moving freely. Only the doppelgangers remain: the dark Mark-double and the luminous Helen on opposite sides of a threshold. The film closes with air-raid sirens and what sound like bombs falling. Bob hears knocking and sees the silhouette of the Mark-double at the door; Helen reacts with dread, refusing to open. Personal and political dissolution fuse into an implied apocalypse.