There's something strange about Martin, and Tess can't work out what it is. He's a Switcher, with the same amazing powers that she has, but there's a sinister side to him. As Tess begins to unravel the awful secret Martin is hiding, she is dragged into the dark night-time world in which he lurks. And there she is faced with the most terrifying choice of her life…A spellbinding story of a girl who has the power to take on animal shape, from bestselling author Kate Thompson.