In Joker, Arthur Fleck falls in love with his neighbor, the down-on-her-luck single mother. Throughout the film, Sophie seems to be one of the only people who actually cares about him. So he’s devastated when he visits her apartment and realizes that their entire relationship has been a figment of his imagination. The film makes the aftermath of this revelation ambiguous, because we don’t find out what happens to his imaginary girlfriend afterwards in the Joker movie.