In the Duchy of Cornwall, a dark sorcerer named Pendragon Torin Thatcher holds sway over giants, witches, hobgoblins, and other shadowy creatures. A wise wizard named Herla defeats Pendragon and banishes him and his followers to a remote, uncharted island. When Herla dies, Cornwall loses its last line of defense, and Pendragon vows a chilling revenge.
Years later, the realm celebrates the coronation of Princess Elaine Judi Meredith, the daughter of King Mark Dayton Lummis. Pendragon arrives in disguise as a foreign lord named Elidoras and gifts Elaine a music box containing a tiny dancing jester. That night, Pendragon peers into Elaine’s bedchamber and magically opens the box, releasing the miniature dancer. The figure grows into a terrifying giant named Cormoran, and the castle guards are powerless to stop him as he abducts Elaine. Cormoran carries Elaine to Pendragon’s ship, where a bumbling henchman named Garna waits. A brave young farmer named Jack Kerwin Mathews comes to Elaine’s aid and defeats Cormoran. In gratitude, King Mark knights Jack and names him Elaine’s defender. As the two begin to fall in love, the King and his chancellor grow uneasy about Pendragon’s looming threat. The King tasks Jack with guiding Elaine to a convent across the sea for safety, but the plan is almost derailed when Elaine’s lady-in-waiting, Lady Constance Anna Lee, bewitched by Pendragon, betrays him and reveals the plan.
Pendragon sends demonic witches to intercept the voyage. The ship’s captain is murdered, Elaine is captured, and Jack wants to pursue, but the crew refuses and flings Jack and Peter, the captain’s young son, overboard. At Pendragon’s castle, Elaine is bewitched again, becoming an evil witch loyal to him; Pendragon returns to Cornwall to confront King Mark. He gives the king a desperate choice: renounce the throne within one week or Elaine will be killed. After Pendragon vanishes, King Mark discovers Lady Constance’s treachery and, standing before a mirror, watches her reveal a witch’s form. A practiced blow shatters the mirror, breaking Pendragon’s enchantment over Constance.
At sea, a kindly Viking named Sigurd Barry Kelley rescues Jack and Peter. He introduces them to the Imp Don Beddoe, a leprechaun imprisoned in a glass bottle by the elves for crafting seven-league boots from a pot of gold. The Imp speaks only in rhymes and explains that his three remaining coins can grant wishes to an honest person. Sigurd possesses the bottle but has not yet earned a wish, signaling he is not honest. In exchange, Jack must free the Imp once the wishes are granted. Jack agrees, and the Imp guides them toward Pendragon’s island.
With the first two wishes, Jack reaches Pendragon’s castle and secures Elaine’s release, though she has already been transformed. On the journey home, Elaine slips Jack a sleeping potion. When she touches the Imp’s bottle, her dark nature heats it and she hurls it into the sea. Pendragon seizes the moment to capture Jack and his companions, attempting to force Jack to reveal the Imp’s whereabouts by turning Peter into a chimpanzee and Sigurd into a dog. Jack, however, does not know where the Imp hides.
Alone with Elaine, she reveals her witch form to him. With help from Peter and Sigurd, Jack escapes and smashes Elaine’s mirror reflection, breaking the spell that bound her.
As the friends flee the castle, Pendragon conjures a two‑headed giant. The Imp’s bottle washes ashore, and he grants Jack’s final wish by summoning a sea monster that destroys the giant. Pendragon answers back by transforming into a dragon and attacking the ship. After a fierce duel, Jack kills Pendragon, and the castle collapses, crushing Garna and the witches. Sigurd and Peter are restored to their human forms. True to his word, the Imp is freed and uses his magical boots to return to Ireland, creating a rainbow that guides Jack and the others home to Cornwall.
