In a world full of the sick and dying, the hurting and desperate, and those lost in darkness, angels dwell. Messenger angel Sarah is focused, dedicated to the cause of heaven in the war against hell. For centuries, she has watched other angels succumb to temptation and break the rules governing relationships between angels and humans. Sarah has vowed to never become one of the 'Fallen' angels, now demons cursed to wander the depths of hell for eternity. She knows that she is stronger than the others, incapable of emotional attachment and the feelings of love and desire that can be so dangerous to her kind.

Jackson Bennett is alone in the world, and he prefers it that way. The former Army sergeant has seen more death than any human ought to experience in one lifetime. Even his dreams are haunted by the faces of those who have lost their lives because of him. He feels lost, purposeless, until an encounter with an angel reveals the secret purpose that he was made for. Born of a superior race of humans, Jackson learns of a special assignment. Should he accept, he will become an important part of world that exists between heaven, hell, and earth. After all that he has been through, Jackson doesn't know if he's ready to take on such a heavy responsibility; what he does know is that he could lose himself in the eyes of Sarah, the intriguing angel assigned to him. She is the only person who seems to understand the darkness and pain that have enveloped his heart; she is the only person capable of driving them away.

In a battle between love or loneliness, divinity or damnation, Sarah's choice once seemed easy. What she finds is that the black and white lines that once defined her world are now impossibly blurred and gray. What she finds is that she may not be not quite as strong as she thought.