Brendan Gleeson will be joining Joaquin Phoenix and Lady Gaga in Todd Phillips’ sequel film, Joker: Folie à Deux, Deadline reports.

Phillips is returning to direct and co-wrote the script with Joker scribe Scott Silver, whose work on the 2019 film earned him an Academy Award nomination for Best Adapted Screenplay. Little is known about the sequel, though sources report it will have musical elements and be set in Arkham Asylum, where the first film left Arthur Fleck (Phoenix).

Lady Gaga is thought to play Harley Quinn, the Arkham psychiatrist who falls in love with the Joker and becomes his partner in crime, with Zazie Beetz also confirmed to be returning to her role as Arthur’s (former) neighbour, Sophie. Any details on the plot, how the musical elements might be incorporated, or who Brendan Gleeson will be playing are, predictably, being kept top secret.

Gleeson was recently seen in Joel Coen’s The Tragedy of Macbeth, and will next appear opposite Colin Farrell in Martin McDonagh’s The Banshees of Inisherin, premiering at Venice Film Festival. The three previously collaborated on In Bruges.

The Warner Bros. and DC film is scheduled to begin filming this December; Joker: Folie à Deux is set to be released October 4th, 2024.