If this doesn’t give you chills, you should probably check your pulse. This woman’s voice is one of the treasures of our time. (Oddly enough, her early reputation was made as a virtuoso fiddler at the age of 10. Her voice matured gradually.)
The story told in the song is known as Lost Children of the Alleghenies: George and Joseph Cox (ages 7 and 5), who disappeared in the woods and kicked off a massive search only to be found (as the lore goes) by the dream of a local farmer.
Beauty and sorrow are such a powerful mix. Johnny Cash, for example, would have imbued this song with a deep gravitas. Alison Krauss, on the other hand, imbues it with a profound sense of tragedy that resonates all the more because of the lightness and delicacy (not to mention the sheer skill) of her vocal line.