Eighteen years have passed since Angel, the prehistoric Carcharodon megalodon shark, broke free of the Tanaka Lagoon and returned to the depths of the Mariana Trench. Meanwhile, Jonas Taylor, the famed adventurer who captured the Meg shark, has become Jonas Taylor, middle-aged father of two, overwhelmed by mountains of bills and the daily strife of raising a family. But his life is about to change.

A prehistoric shark surfaces off California and proceeds to wreak havoc. Sixty feet long, it is a member of a species living in the ocean depths for the last 100,000 years. Jonas Taylor, a paleontologist and deep-sea submariner, tries to capture it for an aquarium.