The Castilian title of this film says it all. The story he tells The hardest decision is indeed a crossroads more terrible, tragic and painful that can go through a family: the acceptance of the death of one of its members. In this case, it is also witness the agony of Kate (Sofia Vassilieva), a girl who from early childhood suffer a rare form of leukemia and the fight of his mother, Sara (Cameron Diaz) to keep it alive.