In every alley in the city of Chicago, you can find a bright yellow poster with a mean-looking rat under a red cross hair, warning you of how dangerous rats are and to alert you that exterminators have planted rat poison in the area. Printed in bold red letters on the poster is the slogan, "IF RATS CAN'T FEED, RATS CAN'T BREED."
In this game, you will be playing as the head of a family of rats trying your best to survive in this hostile environment. You must lead your family to victory by scavenging for food to feed your rats, then breeding to produce more rats, and establishing new nests to grow your territory. Finally, you must become Da Big Cheese to control Rat City at the heart of the underground. But beware! In the big city, a rat can meet danger around every corner!
—description from the publisher