More details for the sequel film Joker: Folie à Deux have been revealed, and it appears that the action may take place in an infamous location in the Batman universe.
In a report by The Wrap, the sequel will more likely take place in Arkham Asylum, a psychiatric hospital in Gotham. In a separate report made by Dateline, they pointed out that “Folie à deux” is a French reference to a medical term where “a mental disorder which affects two or more people”.