Joaquin Phoenix returns alongside Lady Gaga in Joker: Folie à Deux, the sequel now getting an international cinematic release in October.

You may find yourself watching Joker: Folie à Deux wondering if its subtitle (which roughly translates as "a shared madness") applies to the characters or the filmmakers.

Todd Phillips' sequel to his 2019 hit Joker, which brought Joaquin Phoenix an Academy Award in the title role, is a big swing: It's a courtroom drama/musical, in which Phoenix's incarcerated madman Arthur Fleck/Joker meets up with the equally deranged Harley Quinn (here called Lee, and played by Lady Gaga) as he's about to stand trial for murder, and they express their mutual love and nihilism by singing a lot of midcentury classic songs to each other, very slowly.

It's an odd decision, to put it mildly.

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It's not that musicals can't effectively explore darkness (see Sweeney Todd if you doubt); it's that in order to do so, you have to let people actually sing.

Lady Gaga is possessed of a gloriously swooping voice that's at home in any style of song, but here she spends much of the movie croaking out lyrics in a cramped, scratchy whisper. It makes sense for the character – Lee, who's in a psychiatric hospital, is clearly deeply disturbed – but it's a waste; why not give us a few more fantasy sequences and really let her sing?

Phoenix, a passable if small-voiced singer, likewise fails to soar (though – who knew? – turns out he can tap-dance).

What both of them ultimately prove is that songs like That's Entertainment and What the World Needs Now and If My Friends Could See Me Now can sound thoroughly creepy if you slow them way down; this is, perhaps, not enough of a reason to make a movie.

Taking place a few years after the events of Joker, this movie finds Arthur imprisoned, mocked by guards ("You got a joke for us today?') and, denied his customary Joker makeup, unable to be his true self.

But he finds a piece of that self in Lee, who locks eyes with him in a rehab singing class with psychiatric patients (no, it makes no sense that he'd be allowed to do such an activity) and promptly declares her love.

"Are you crazy?" he asks her, admiringly. The film alternates between elaborate fantasy sequences, with Joker and Lee as a sort of deranged Fred and Ginger, or Sonny and Cher, and the rather more grim reality of the trial.

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There's plenty of talent on screen here, which makes Folie à Deux all the more maddening; a scene in which Lee applies eyeliner while warbling I've Got the World On a String is a mesmerizing reminder of Gaga's uncanny charisma. But ultimately, it's a wild experiment that mostly falls flat.

"I don’t want to sing any more," says Joker, near the end; not soon enough.