The protagonist Harris manages to save the school he teaches at from a massive swarm of the giant mutant rats through a combination of quick thinking and the use of anything he can use as a weapon; after getting all the staff and teachers to barricade themselves in the top classroom, he kills several rats using chair, a poker, and his own feet as clubs, and even drowns one in an aquarium. He then helps co-ordinate with the emergency services in keeping the rats at bay until the pest control guys show up and gas them. The results? Only two casualties (the headmaster and a police sergeant), and he himself is relatively unscathed.
After finding the rats' original lair, the cellar of an abandoned canal house, Harris fights and manages to kill two rats which are even larger and stronger than the other mutant rats, losing two fingers and an earlobe in the process, before discovering the dominant mutant and finishing it off.
A minor character, Henry Sutton, a quiet little man is on a train which is held up by a rat attack. The train catches fire at the front, and more rats attack from the rear, devouring passengers alive. Henry manages to escort the two ladies he was sharing his carriage with (one of whom is near hysterics) to safety, never once loosing his head.