Inspired by the rags to riches (to rags) real-life saga of Scottish rap duo Silibil N' Brains, a.k.a. Gavin Bain (Séamus McLean Ross) and Billy Boyd (Samuel Bottomley), James McAvoy's crackling directorial debut follows the unexpected journey of two lifelong friends from Dundee who dream of hip-hop super-stardom. There's just one problem: nobody takes two white guys with thick regional accents seriously in the UK's early 2000s rap scene, especially not the London gatekeepers who laugh them out of an audition.

Back home and humiliated, the pair hatch a plan so absurd it just might work: they'll reinvent themselves as hard-partying MCs from Southern California - complete with fake backstories and (barely) convincing American accents. Against all odds, their career explodes, conning even one of the industry's top producers (McAvoy), who quickly signs them to a major record deal.

Unfortunately, keeping up the lie without losing sight of who they are becomes harder as the stakes rise, as each new day threatens another fall from grace.