Everyone in Foss Butcher's village knows what happens when the magic-workers come; they harvest human hearts to use in their spells. That's just how life in her kingdom works. But Foss, plain, clumsy, and practical as a boot, never expected anyone would want hers.

When a sorcerer snags a piece of Foss's heart without meaning to, she is furious. For once a heart is snagged, the experience is ... well, unpleasant. So, Foss finds herself stomping toward the grand City to keep his enchanted House and demands that he fixes her before she keels over and dies, or whatever happens when hearts are Snagged.

But the sorcerer, Sylvester, is not what she expected. Petulant, idle, and new to his powers, Sylvester has no clue how to undo the heart-taking, or how to do much of anything really, apart from sulk. Foss's only friend is a talking cat and the walls themselves have moods.

As Foss searches for a cure, she accidentally uncovers that there is much more to the heart-taking - and to the magic-workers themselves - than she could have ever imagined...