When an old castle needs repairs, it's time to call Bob the Builder! Unfortunately a case of mistaken identity puts Bob's father in charge, resulting in one disaster after another! Meanwhile, tales of Camelot inspire Bob's noble crew of machines - Sir Lift-A-Sot, Sir Roll-A-Lot and Lady Mix-A-Lot - in their quest to get the job done. And Sir Spud-A-Lot finds a suit of armor and a fiery steed almost perfect for jousting! Back at the castle, Bob's father is a bit of a royal pain, locking himself and Bob in the dungeon and then finding himself mysteriously trapped in a maze! Finally, a medieval pageant celebrates the grand opening of the castle and a great father-son relationship.