When Madlyn and Rollo are sent to stay at ancient Clawstone Castle, they soon fall in love with the house and its eccentric, penniless inhabitants. There's grumpy, limping Uncle George, mousey Miss Emily, and reclusive Cousin Howard who hardly ever leaves his library.

But, the children are especially enchanted by the Cattle of Clawstone Park - rare and beautiful beasts, as white as snow and as wild as wolves. No one knows where they came from, but the owners of Clawstone have always protected them. So, as the castle crumbles away, Madlyn and Rollo devise a money-raising scheme...