Needing to put distance between herself and a failed relationship, Sara volunteers for a medical mission in a remote region of Afghanistan. There the young American quickly proves her worth, helping deliver babies, tend sick children, and lance boils. It's grueling work, but also rewarding. Sara feels like she's making a difference.

On a rare day off, the medical team hikes into the mountains for some much-needed rest and recreation-only to stumble onto a battle between American forces and Afghani insurgents. In the chaos, all but Sara die.

Alone and injured in the dry ravines of the...