This heroic tale was inspired by a true story that took place over 500 years ago. It tells of Katje the windmill cat who lives happily with Nico, the miller, in a Dutch village by the sea. By day, Katje chases mice in the windmill; by night, she sleeps on a soft pillow on Nico's bed. Then Nico brings home his bride, Lena, and everything changes. Katje is shooed away by Lena as she sweeps the house or when she finds Katje playing with the new baby. Eventually, poor Katje leaves her home and moves into the windmill. But when a storm breaks the dike that holds back the sea, Katje performs a feat of extraordinary courage that makes her forever welcome in the house.