Ol' Rosie, a cranky, old mare, has escaped the corral and has led ten of the Nolan's other horses into the stark mountains of eastern Oregon. It's not the first time, but for Wart's pa, this is a particularly desperate situation. On their ranch -- as on any ranch in 1907 -- horses are the key to a rancher's livelihood. So when Ol' Rosie and the other horses run off, somebody has to go catch them. But Wart's ma is having a baby. His pa needs to stay...