Should you believe what you see with your own eyes, even if it can't be explained? When Laurie is arrested for setting fire to her father's research lab she's unsure what to say in her defence. Should she say that she's an animal rights activist? Or should she tell the whole story, about the mysterious horsemen that she saw in the woods, and the terrifying truth which lay behind their appearance? In the eyes of the police she is a criminal, but Laurie knows that she's a hero. The first time Laurie and her dad see the white rider, watching them from the deep, cool shadows of the trees, he is alone. Laurie is convinced that his appearance has a meaning that somehow he is trying to tell them something - something her dad needs to pay attention to. Is the rider somehow linked to the genetic research into squirrels that Laurie is helping her dad with in the lab? When a second rider appears alongside the first, and then a third, Laurie knows she must try to understand who they are and what they represent. With the help of her brother and his best friend, she discovers what the riders mean, but will it be too late to stop the inevitable chain of events that has been set in motion? Kate Thompson is the winner of The Whitbread Children's Book Award and the Guardian Children's Fiction Prize, and four times winner of the Irish Children's Book of the Year Award.