Millionaire Mason Murphy renovates the haunted Mayhew mansion. He plans a tremendous lunar eclipse viewing party to celebrate his return to his hometown of River Ridge Iowa. At the party, magic runs out of control and the party guests are murdered one by one.

When the prehistoric warm-water beast the Crocosaurus crosses paths with that cold-water monster the Mega Shark, all hell breaks loose in the oceans as the world's top scientists explore every option to halt the aquatic frenzy. Swallowing everything in their paths -- including a submarine or two -- Croc and Mega lead an explorer and an oceanographer on a wild chase. Eventually, the desperate men turn to a volcano for aid.