It is 1845 and a wagon team comprising of three families have hired mountain man Stephen Meek (Bruce Greenwood) to lead them over the Cascade Mountains to the Valley beyond. But when the group follows Meek along a shortcut he claims to know, they find themselves lost in a dry, harsh desert without water. As they continue along their way, conserving water and plagued by the uncertainty of their predicament, they come across a Native American Indian (Rod Rondeaux). While Meek suggests they shoot the Indian, the others believe he may be a more reliable guide than the man they have employed. Emily Tetherow (Michelle Williams) shows herself to be the strength of the group as they struggle against the elements and their lack of faith in each other's instincts for survival.