Sophie thinks of herself as plain and boring, especially compared to her vivacious younger sister Lettie. Sophie expects to spend the rest of her life quietly making hats in the back room of her family's shop, but as her country prepares for war, she is forced to set out on an extraordinary adventure!

Sophie’s excitement continues as she takes up the position of cleaning lady in Howl’s Moving Castle. She soon finds herself at home and making friends with the demon in the fireplace and even the moody Howl. And while horrors of war are edging closer and the magicians of the kingdom turn themselves into terrible monsters to fight the enemy, Sophie finds that what she really needs to fear is Howl’s bathroom!