Clare's brother, Tom, also known as the pied piper, has stolen away the children of Hamelin. But Clare knows that's only half the story. Tom isn't the easiest person to love, but she's certain that he couldn't be so cruel. There has to be a good reason why he stole the Fae Queen's magic pipe and led the children to a faraway land, never to be seen again.

Together with Anna, the mayor of Hamelin's daughter, Clare embarks on a journey into the Faerie Realms. In order to succeed, she will have to dodge faerie traps and stay out of the evil Rat Prince's claws. Only she can save the children of Hamelin and clear her brother's name.

But who will she have to betray to do it?