Jack the Giant Killer is a 1962 American fantasy film loosely based on the British fairy tale of the same name.
The evil sorcerer Pendragon (Torin Thatcher) plots to take over the throne of Cornwall from King Mark (Dayton Lummis). To do so, he uses a giant to kidnap the king's daugher Elaine (Judy Meredith). Before the giant can escape with Elaine, Jack (Kerwin Mathews) heroically saves her and slays the giant.
King Mark plans to protect his daughter by sending her away to a convent, but Lady Constance (Anna Lee) is under Pendragon's spell and reveals the plot to him. He sends witches out to capture Elaine and dump Jack into the ocean. Once Elaine is in his clutches, he uses magic to hypnotize her and transform her into an evil witch.
An old Viking rescues Jack while the King magaes to free Constance from her spell by breaking a mirror. Pendragon threatens to kill Elaine if the King does not step down, but when Jack and his friends try to rescue her, she turns on them. Jack also manages to use the broken mirror trick to free Elaine from her spell.
Pendragon transforms into a dragon and challenges Jack, who slays the beast. Pendragon's empire crumbles and the kingdom is free at last.