 When PCP inexplicably gets into the water supply of a large zoo in Frankfurt, Germany, the zoo animals go crazy, break out of their cages, and go on a homicidal, nightime rampage through the city killing any person they come into contact with starting with sewer rats killing a number of paserbyes, then tigers, cheetahs, lions and even elephants joining in the killing. Zoo vetenarian Rupert Berner, his scientist girlfriend Laura, along with a local police officer, Inspector Braun, try to find a way to control the murderous animals and stop them before they decimate the entire city.