By following the instructions at the bottom of each page, the reader can have several different adventures in the Old West.

    Kirstie and her brother Angus find the egg and take it home. The next day it has hatched into a tiny greeny-grey creature with a horse's head, warty skin, four flippers and a crocodile's tail. The baby sea monster soon becomes the family pet – but the trouble is, it just doesn't stop growing!