In the 1980s, a group of homeless people living in the underground of New York City become mutated due to toxic waste that has been dumped in the sewers. The mutants, known as C.H.U.D.s (Cannibalistic Humanoid Underground Dwellers), start attacking and killing people in the city. A police officer and a photojournalist team up to investigate the disappearances and stop the C.H.U.D.s before they wreak havoc on the streets of New York.
When a military experiment goes wrong, a mutant zombie is unleashed on a high school, causing chaos and terror.