Vicky Bell and her brother Johnny live in New Zealand at the turn of the century. Their father is a local farmer who helps out when a ship belonging to Mr Lindsay, a rich importer who lives near them, is wrecked on the coast. A prize bull being imported on the ship escapes and swims to land. Vicky and Johnny and their friend Carrie, who is Mr Lindsay's daughter, find the bull in an unexplored valley in the bush and trap it, but there are many complications about catching it, not the least of which is that Carrie's governess and Vicky and Johnny's Aunt Clara do not approve of girls taking part in adventures of this kind.