In Edinburgh washed up country-and-western singer John McGuire is broke and his family is emigrating. He and grandson Billy share the same dreams. They run away together in search of John's wealthy American ex-co-star Betsy Hall.

King Arthur, accompanied by his squire, recruits his Knights of the Round Table, including Sir Bedevere the Wise, Sir Lancelot the Brave, Sir Robin the Not-Quite-So-Brave-As-Sir-Lancelot and Sir Galahad the Pure. On the way, Arthur battles the Black Knight who, despite having had all his limbs chopped off, insists he can still fight. They reach Camelot, but Arthur decides not to enter, as "it is a silly place".