A game warden moves his family to Lake Placid, once the site of deadly crocodile attacks. Locals assure him the crocs are gone, but his mischievous young son finds a few baby crocs and begins feeding them. They quickly grow into very big adults and start attacking the game warden's family and nearby town.

A westerner named Casey, studying Ninjutsu in Japan, is asked by the Sensei to return to New York to protect the legendary Yoroi Bitsu, an armored chest that contains the weapons of the last Koga Ninja.