Brian Wilson (Dano) sits at piano talking to someone off camera. He’s working on a song that will turn up on his 1966 masterpiece Pet Sounds. "What if I lose it and never get it back? What will I do then?" he wonders. This - fragility, insecurity, talent - is what’s explored in Love & Mercy, Bill Pohlard’s brilliant biopic of The Beach Boys’ songwriter.

After an inventive credits sequence that takes The Beach Boys through their surf and striped shirts period, the story kicks off just as Brian begins writing 'the greatest album ever made.' Holed up in the studio and experimenting with drugs, the music he’s writing is wholly original but his band aren’t sure and it begins to eat away at his confidence. Fast forward to 1985 and a heavily-medicated Brian (Cusack), now a shell of the man he was, is in the care of manipulative therapist and legal guardian Eugene Landy (Giamatti) but new flame Melinda (a luminous Banks) gives him the strength to make those first tentative steps to independence...

The structure of two dovetailing stories exploring Brian’s struggle to express himself makes this biopic a standout. One story has Brian at his creative peak but about to descend into a nightmarish mental struggle while the other sees him make overtures to emerge from that hell and get back to recording again. The link between the two Brians aren’t immediately noticeable but Pohlad works hard to find lines, expressions or gestures that hand the stories baton-like back and forth.

But where Pohlad really excels is getting into Brian’s head during the creative process. Cutting to black, or focusing on Brian’s dazed face, we hear half-formed ideas and fragments of songs zoom in and out of the mix: impossible overdubs, distorted strings, angelic harmonies, hints and echoes of songs that will become Cabin Essence or I Know There’s An Answer all layered on top of each other. A big shout out to sound mixer Edward Tise here.

Dano’s face as he lets these beautiful sounds filter through his mind captures the serenity of the music but also the fear that they may forever be stuck in his head. Later, Pohlard uses sound as an enemy that turns on Brian: he hears terrifying screams in his headphones and a dinner with friends turns hellish as the clanging of cutlery reaches a chaotic cacophony.

Dano is terrific in the role. The puppy fat, the awkward stance of arms stuck to his side, he looks like a little boy that’s been told off; when Mike Love (Jake Abel) is less than impressed with the new material, telling Brian that he’s let his family down, you just want to hug him. Cusack, despite looking nothing like Wilson, isn’t too shabby either - a performance of shifty awkwardness, like his skin is itchy but he’s not allowed to scratch. Musos will get a kick out of the factually accurate depictions and the highlighting of the Wrecking Crew’s contribution to the Pet Sounds sessions.

But Love & Mercy doesn’t have it all its own way. There are some ropey moments towards the close, Murry Wilson’s (Bill Camp) dialogue is loaded with dramatic irony - "In five years no one will remember The Beach Boys!" - and Giamatti, strong turn aside, is too monstrous and omnipresent. He might as well where a t-shirt that reads Bad Guy.

But that’s nit-picking. Love & Mercy is a strong and inventive biopic.