Justin (Freddie Highmore) lives in a kingdom where bureaucrats rule and knights have been ousted. His dream is to become one of the Knights of Valour, like his grandfather was, but his father Reginald (Alfred Molina), the chief counsel to the Queen (Olivia Williams), wants his son to follow in his footsteps and become a lawyer. After an inspiring visit to his beloved Gran (Dame Julie Walters) and bidding farewell to his supposed lady-love Lara (Tamsin Egerton), Justin leaves home and embarks on an adventurous quest to become a knight against all odds.