Raúl, a solitary and obsessive 60-year-old foley artist, lives austerely in an apartment full of curious objects, where he feeds an obsession with his neighbor, whom he films in secret and then reproduces the sounds of her life through foleys. Despite remaining hidden, he begins to develop a one-sided relationship from the distance with this woman, whom he calls Lucy. After several sessions, on day 13 of his project, Raul discovers Lucy finding evidence of her husband's infidelity. After fighting and throwing him out of her house, Lucy suffers intensely from the breakup, which Raúl takes advantage to film her and bonds with her, pretending to approach her emotions. Raul is convinced that the window of opportunity is now open and he believes that a sad and vulnerable Lucy, might be his. He wants to become the architect of the sounds of her life and somehow he begins to feel that she enjoys the imaginary company that he gives her.
In this climax of compatibility between them, Lucy's husband returns home unexpectedly. She loses the determination of her initial annoyance and lets him stay. However, she continues to be sad and indifferent to the return of her husband, who tries to recover his place and return to the routine of his marriage. Devastated, Raul intends to persuade her, crossing to her door with the intention to remind her about the connection they now have. The amorous delirium leads him to be confronted closely by what is behind his obsession: Lucy's true identity.
Tormented by what he has just discovered, he returns home distressed and gets rid of all traces of Lucy, at that point, we discover that his obsession is greater than we thought.