Heaven refers to them as Misplaced Halos.

Humans don't even know they exist.

This faction of celestial warriors was sent here under the cover of darkness to protect humanity from Lucifer's demons. In return for their servitude, these warriors expect only one thing: the love they were promised, what angels refer to as an amsouelot.

The first of his kind, Obsidian has spent the past fifteen hundred years fighting alongside his brothers, protecting humans from Lucifer's demons, all while keeping to the shadows. Their mission is simple, right up until it isn't. The day Obsidian learns of a traitor in Heaven is the day everything changes. The entire reason for his existence is put on hold because there's a new assignment: find the female whose soul belongs to his and protect her, no matter the cost.

Penelope Calazans spends her days sleeping and her nights serving free drinks to the gamblers looking to win big in Sin City. It's not a glamorous life, perhaps a tad lonely, but she's content. Or she thought she was. Then he appears. The mystery man who would turn out not to be a man at all, but rather an angel. The angel who would turn Penelope's mundane life upside down, revealing what really lurks in the dark.

Not only do they have to battle the demons looking to possess their souls, but Obsidian and Penelope must overcome the obstacles that come with falling in love. In the end, an angel and a human must make the ultimate sacrifice, all in the name of a love everlasting.