Felix, a blood-covered man in Berlin, seeks warmth and shelter in a woman's apartment. He hides there, becoming an invisible guest, and gets to know the woman's life. Felix discovers a conflict between her and her estranged father. As he eventually leaves the apartment, they meet outside, fall in love with each other, but a revelation about the spare key he kept destroys their trust. The story follows their emotional journey as they confront their past and reconcile.