Faeries disappeared over one hundred years ago, as suddenly as slipping through a doorway. It was only the very foolish, or the very determined, who held out hope for their return. In the wake of World War I, the world is a decidedly unmagical place. Mouse Dunne once dreamed of becoming a Faerie anthropologist, but with one telegram, her world shattered. At the Somme, her cousin Bertie’s body disappeared into the mud, and her brother Roger came home with devastating shell shock. It was time, she knew, to put aside childish dreams.

Then Mouse receives news that her uncle has left her Thistlemarsh Hall, a crumbling manor in the English countryside, once blessed by the Faerie King himself. But there is a catch: if Mouse does not rehabilitate the house in one month's time, she will forfeit her inheritance and any hope of caring for her brother.

It looks impossible, until a mysterious Faerie appears with a proposition. Mouse knows better than to trust a Faerie – especially one so insufferably handsome and arrogant – but she is out of options. There are wild and magical forces at work in the house, and Mouse must confront the ghosts of her past... or lose everything.