Captain Flint is the notorious pirate who amassed a legendary treasure hoard and hid it on a remote island. He engineered an elaborate safeguard for his riches, designing a mechanism to drain a volcanic crater lake, thereby revealing his sunken ship laden with wealth. His entire legacy revolves around this concealed treasure, which serves as the central driving force of the narrative.

His familial connection exists through Kathy, identified as his granddaughter. She actively pursues his treasure map, seeking to claim her inheritance and asserting her position as Flint's rightful heir. This lineage forms part of her core motivation throughout the story.

Flint himself does not appear directly in the narrative; his actions and influence precede the story's events. His enduring presence manifests solely through the treasure map he created and the intricate engineered safeguards protecting his hidden hoard.