Zaat 1971

In his laboratory, mad scientist Dr. Kurt Leopold, Marshall Grauer contemplates his former colleagues’ derision of his formula ZaAt, a compound that can transform humans into sea creature hybrids. He injects himself with the serum and immerses himself in a tank, emerging as a catfish-like monster, Wade Popwell. In his new form, Leopold releases walking catfish across the town’s lakes and rivers, and releases Zaat into the water supply, rendering many of the townspeople ill. Meanwhile, Sheriff Lou Krantz, Paul Galloway and marine biologist Rex Baker investigate strange occurrences with the local catfish and waterways.

Leopold turns his attention to killing those who mocked his work. He murders former colleague Maxson and his family on a boat, followed by associate Ewing in his home. Afterward, Leopold kidnaps a young female camper, Nancy Lien, at a lake. Taking her back to his lab, the doctor straps her into a mesh basket beside a large water tank, with the intention to make her his mate. However, due to her struggles, the equipment malfunctions, and her corpse, partially transformed, is pulled from the tank.

Baffled by the deaths, Rex contacts an organization known as INPIT, which dispatches scientists Martha Walsh, Sanna Ringhaver, and Walker Stevens, Dave Dickerson, to investigate. Following the kidnapping of Martha, Leopold heads again toward his lab, surreptitiously followed by Walker, who has picked up Leopold’s radioactive trail. The doctor arrives at the lab with Martha, where Rex and Lou happen to be searching. Lou attempts to apprehend Leopold outside his laboratory but is killed in the process; inside, Rex also tries to stop the doctor as he prepares Martha for her transformation. After seriously wounding Rex, he injects Martha with Zaat, readies her to be dunked into the tank, and makes his getaway with canisters of the compound. Martha’s transformation fails, and she is saved from the tank by a dying Rex, though she appears to be in a trance and immediately follows Leopold into the sea.