Joaquin Phoenix Returns as the Joker in "Joker: Folie à Deux" Behind-the-Scenes Photos

The plot details for "Joker 2" are being kept under wraps, and very little is known thus far. However, the teased movie title could offer some insight into the story.

The sequel's title may hint that the Joker will experience this mental disorder alongside his iconic comic-book partner in crime, Harley Quinn. While the first movie delves deep into the psyche of Arthur Fleck and shows his transformation into the violent villain, Joker, the second movie might explore his troubled on-and-off relationship with Harley as they both bring out the worst in each other.