On a moonlit night in a distant research laboratory, scientists make a discovery that could revolutionize modern medicine, but at the same time could cause deadly consequences. The researchers create a chemical substance to detect cancer cells and to destroy them. Experiments are conducted on rodents. An accidental leak of the tested substance from a waste container occurs. It ends up in the basement... Now the white mice in the upstairs laboratory are not the only rodents in the building taking part in the experiment. The enormous rats from the basement also become unwilling volunteers, mutating under the influence of the substance... The unsuspecting Professor Schulz continues the experiment. He administers different doses of the substance to three different rodents to destroy cancer tumors, and the leftovers are discarded again into the ill-fated broken container. Something terrible follows. The invented substance was programmed to detect and destroy cancer cells, and now the rats are programmed to detect and destroy humans... The night of horror, the night of killer rats, has begun.