McKenna Barney is trying to hide her worsening eyesight and has been isolating herself for the last year. But at the request of her little sister, she signs up for a commemorative mail run race in the Canadian wilderness-a race she doesn't know if she can even see to run. Winning would mean getting her disease-and her sister's-national media coverage, but it would also pit McKenna and her team of eight sled dogs against racers from across the globe...