This plot summary is based on a text published ca. 1760 by John Cotton and Joshua Eddowes, which in its turn was based on a chapbook ca. 1711, and reprinted in 'The Classic Fairy Tales' by Iona and Peter Opie in 1974.
The tale is set during the reign of King Arthur and tells of a young Cornish farmer's son named Jack who is not only strong but so clever he easily confounds the learned with his penetrating wit. Jack encounters a cattle-eating giant called Cormoran (Cornish: 'The Giant of the Sea' SWF:Kowr-Mor-An) and lures him to his death in a pit trap. Jack is dubbed 'Jack the Giant-Killer' for this feat and receives not only the giant's wealth, but a sword and belt to commemorate the event. Another giant named Blunderbore vows vengeance for Cormoran's death and carries Jack off to an enchanted castle. Jack manages to slay Blunderbore and his brother Rebecks by hanging and stabbing them. He frees three ladies held captive in the giant's castle.