A message has traveled via the mouse network to cat brothers Anton and Cecil. Their friend Hieronymus has been captured. Though he'd rather stay close to home, Anton is determined to save the brave little mouse who once saved him. Cecil is quick to action, too, but it's adventure he craves.

Boarding one of the machines the mice call "landships"--noisy, smoke-belching trains--Anton and Cecil travel to the heart of the Wild West. Along the way Cecil is tossed out by the train's conductor, only to face huge bison, chattering prairie dogs, and the most dangerous creature of all, a boy who wants to make Cecil a pet. Meanwhile, Anton's search leads him to stampeding herds, menacing rattlesnakes, and fierce, enormous wild cats.

In this perilous territory, do Anton and Cecil have the courage and wit to find and save Hieronymus?