Jon (Domhnall Gleeson) is an aspiring but not-at-all-talented songwriter who impulsively joins an experimental pop-noise band that is in sudden need of a keyboardist. Thus, he finds himself trapped in an Irish cabin for months with the band's mostly asocial members, including the depressive Don (Scoot McNairy) and the angry Clara (Maggie Gyllenhaal).
The band revolves around Frank (Michael Fassbender), a deeply sensitive artist and a musical genius who can instantly compose a song about a "lone standing tuft" of carpet. It should also be noted that Frank wears a giant fake head — always. Frank is enigmatic, but also kind and charming. (Jon rightly wonders: "What goes on inside that head inside that head?") Tensions arise when Jon pushes the group toward "success" — recording music, using social media, playing a gig — thereby disrupting the band's fragile equilibrium.
There's not a lot of plot in Lenny Abrahamson's offbeat comedy. The story, written by Jon Ronson, is loosely based on the late English musician Chris Sievey, who performed as "Frank Sidebottom" (wearing a giant fake head), as well as other outsider musicians. It's a gentle and, at times, provocative exploration of what defines art, what meaning it offers for an audience and the performer, and by what metrics success is measured. The film's conclusion is a beautiful dialogue-free scene that perfectly encapsulates and resolves all these tensions.
Along with its giant head, the film also has a big heart. It's frequently funny, and has a great cast. And then there's Fassbender: The actor spends 95 percent of the film with his own critically lauded head inside a fake one, and yet his portrayal of Frank is extraordinarily rich, engaging and heartbreaking. They should give him a special Oscar with its own giant fake head.