Major Grace Samuels, a trauma surgeon deployed to Afghanistan, spends her life helping her fellow soldiers overcome disease and combat injuries. But her own wounds are harder to heal. Racked with guilt over the death of a fellow soldier, she finds comfort in her only friend and appointed bodyguard, weapons sergeant Jacob "Sharp" Foster. 

Sharp feels more for Grace than a soldier should, more than he wants to admit. When the team discovers a new, quick-to-kill strain of anthrax, he tries to focus on the mission to find its source. He knows he can help Grace defeat her demons, but first they must defeat the deadly outbreak. 

Sharp is Grace's most loyal ally, but in close quarters, he starts to feel like more. She can't watch someone else she cares about die—but she might not have a choice. The closer they get to finding the source of the strain, the closer it gets to finding them.