JOKER: FOLIE À DEUX
In an animated sequence, Joker is impersonated by his shadow, who acts violently and takes his place to perform his singing number for a TV show, and then abandons him on stage before three police officers arrive and attack him.
Arthur Fleck is in custody at Arkham State Hospital awaiting trial for the crimes he committed two years prior.[c] His lawyer Maryanne Stewart plans to argue that Arthur suffers from dissociative identity disorder and that his Joker personality is responsible for the crimes. At a music therapy session, Arthur meets Harley "Lee" Quinzel, who claims that she grew up in the same neighborhood he did, had an abusive father who died in a car crash, and was imprisoned after burning down her parents' apartment building. Lee also expresses her admiration for Joker's crimes and personality.
During a film screening, Lee starts a fire. She and Arthur are caught trying to escape, and Arthur is placed in solitary confinement. Lee visits him to say she is being released to avoid his influence but promises to attend his trial. She asks him to stop taking his medication, and they have sex before she goes. During an interview with television personality Paddy Meyers, Arthur sings to Lee through the TV screen, deepening her love for him.
On the day of the trial, Assistant District Attorney Harvey Dent calls witnesses who dismiss Arthur's claims of insanity. During a break, Maryanne reveals that Lee was actually a psychiatry student who grew up in the Upper West Side, and her father, a doctor, is alive. Furthermore, she voluntarily committed herself at Arkham, checked herself out, and never burned down an apartment building. When Arthur confronts Lee, she confesses that her lies were an effort to get close to Arthur but also tells him that she is pregnant from their night together and has moved into his old apartment building to create a home for them.
At the trial the next day, Arthur dismisses Maryanne and represents himself. After bringing Arthur's former co-worker Gary Puddles and neighbor Sophie Dumond to the stand, Harvey rests his case. Visibly affected by Gary's testimony, Arthur offers no defense. During his speech, he mocks the Arkham guards and indicates that they abuse him. Returning to Arkham, he is taken to the showers by head guard Jackie Sullivan and two guards in retaliation, where he is beaten and brought to his cell partially naked. An inmate and friend of Arthur's named Ricky verbally confronts the guards, resulting in Jackie strangling him to death.
During his closing argument in court the following day, a devastated Arthur renounces his Joker persona, taking full responsibility for his actions. Enraged at this, Lee storms out, and the jury finds Arthur guilty of murder. As the foreperson reads the verdict, a car bomb explodes outside the courthouse, killing and injuring numerous attendees and scarring half of Harvey's face. In the chaos, two followers help Arthur escape, but he abandons them when he realizes they only see him as Joker.
Arthur wanders through Gotham City and encounters Lee on the stairs outside his old apartment, but she rejects him for renouncing his Joker persona. As she leaves, the police apprehend Arthur and bring him back to Arkham.
The next day, one of the guards tells Arthur he has a visitor and is led down an empty hallway. A young inmate stops Arthur and begins telling a joke before repeatedly stabbing Arthur in the abdomen with a shank. As Arthur lies there bleeding to death, he has a fantasy about Lee while the inmate, laughing hysterically, carves a smile on his own face.
