The script tells the story of Jack, a farmer's son in Cornwall who kills the giant Cormoran who has been terrorizing the local villages. After killing Cormoran and claiming his treasure, Jack becomes known as "Jack the Giant Killer." However, this draws the attention of another giant named Blunderbore who vows revenge on Jack if he ever finds him. The story sets up Jack's coming encounter with Blunderbore in the woods near the giant's enchanted castle.