Truthfully, outside the songs, she isn’t given a great deal to do – but within them she’s creepily magnetic, most of all during a prison-visit rendition of The Carpenters’ Close to You, which the singer-turned-actress reimagines as a spidery anthem of romantic obsession.
Despite its title, though, Folie à Deux’s unapologetic sole focus is Phoenix – who is again transfixingly unsettling, right from our shocking first glimpse of him lurking in his cell, where he less resembles a human being than a crumpled Post-it note.
Bullied and patronised by the guards, led by an imposing Brendan Gleeson, Arthur is as stony-faced as Buster Keaton. (It can’t be a coincidence that he has the pageboy haircut to match.) In court, however, his showboating Joker persona starts breaking back through, as his followers bay for the sequel to which they feel entitled.
As a repeat performance – even a cunningly subversive one – Folie à Deux can’t quite match its predecessor for dizzying impact. But it matches it for horrible tinderbox tension: it’s a film you feel might burst into flames at any given moment.
Cert tbc, 138 min. Screening at the Venice Film Festival; in UK cinemas from Friday October 4