When Ballister Boldheart (Riz Ahmed), a knight in a futuristic medieval world, is framed for a crime he didn't commit, the only one who can help him prove his innocence is Nimona (Chloë Grace Moretz), a mischievous teen with a taste for mayhem - who also happens to be a shapeshifting creature Ballister has been trained to destroy. But with the entire kingdom out to get him, Nimona's the best (or technically the only) sidekick Ballister can hope for. And as the lines between heroes, villains, and monsters start to blur, the two of them set out to wreak serious havoc - for Ballister to clear his name once and for all, and for Nimona to...just wreak serious havoc.