If the first “Joker” asked if we could have empathy for the devil, the sequel questions if we're ready to watch him fall in love, go through the emotional wringer and also put on a show.

Co-written and directed again by Todd Phillips, “Joker: Folie à Deux” (★★½ out of four; rated R; in theaters Friday) takes bigger swings than its audacious 2019 predecessor, a best picture nominee and the highest-grossing R-rated movie in history until Deadpool and Wolverine teamed up. It even has its own dynamic duo, with Joaquin Phoenix’s tortured Joker finding a soulmate in Lady Gaga’s electric take on Harley Quinn.

Not everything hums around them, as the dour and distracted but still well-acted “Folie à Deux” attempts to be prison drama, courtroom thriller and supervillain musical all at once. With Gaga belting old-school pop standards and Phoenix tap-dancing like a madman, at least one of those aspects definitely works.

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It’s been two years since failed party clown/comedian Arthur Fleck (Phoenix) became a folk "hero" of sorts in Gotham City, putting on garish face paint and getting locked up at Arkham State Hospital for five murders (including blowing away a late-night host on live TV). TV movies and books have kept his legend alive outside prison walls, but inside, the grim and emaciated Arthur has lost his signature cackle. He listlessly takes his meds and gets hounded by mockingly merry prison guard Jackie (Brendan Gleeson) to tell jokes.

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Arthur’s highly anticipated trial is about to start and with the state going for the death penalty, his lawyer (Catherine Keener) wants to mount an insanity defense and argue that it was a Joker “personality” that did these killings, not Arthur. His mind becomes more interested in matters of the heart: In music therapy at Arkham, he meets Lee Quinzel, a disturbed songbird who set fire to her parents’ apartment building and is a big Joker fan. She tells Arthur that after seeing him kill a guy on national television, “I didn’t feel so alone anymore.”

Like in the first film, Arthur has showbiz fantasies in his head but they now feature him dueting with Lee on songs like the Bee Gees’ “To Love Somebody.” The two share a musical connection in his real life, too, gently whispering “Get Happy” lyrics to one another. She’s freed from the minimum-security ward to get her away from his “bad influence” but plays a major role as Arthur and her alter ego see their day in court.

Phillips crafts a compelling narrative early on, contrasting gritty, cruel jail scenes with Arthur finding real happiness for the first time in his life. That momentum screeches to a halt once we get to the showy trial, as the “Folie à Deux” then turns into an unnecessary retelling of the original movie, with certain returning characters and plot points. It does give Arthur a few moments of actual contrition, and Phoenix inexplicably channels Foghorn Leghorn when he decides to mount his own defense.

That first “Joker” leaned nihilistic and toxic, if deep in its own psychological way. The sequel is also dark but there’s a hope and sweetness to it at times. That spawns from the strong chemistry between Gaga and Phoenix in quiet moments and in energetic song-and-dance numbers, as they rip through the Great American Songbook and tunes such as “The Joker” (the Anthony Newley one, not the Steve Miller Band). Anyone familiar with Batman comic-book lore knows Joker and Harley have their extreme ups and downs, and it’s enjoyable here to watch Arthur and Lee’s bad romance come to fruition.

While “Folie à Deux” embraces a heightened, even cartoonish quality in continuing the story of Phoenix’s troubled soul, Phillips really misses a chance to go full musical and do something truly different. Just dipping its toes in that genre, with those strong performers, is enough to drive you mad.