Werewolves, vampires, and other preternatural creatures have been living in relative peace with humanity for the past twenty-six years. There are other monsters that humanity doesn't know of, but it's best kept that way.

Valkyrie Dalton is one of these monsters. As a hellhound for Cerberus, she marks souls for the Greek underworld. When she's not gifting people with the 'kiss of death', or drinking away her problems, she's solving cases as a detective for the Las Vegas Preternatural Crime Unit. After all, it takes a monster to catch one.

When headless, heartless bodies start appearing, Val's forced to get close to her new partner, Jack Khoury. He's blunt, forward, and way too hot for his own good. As they spend more time together, the mental walls she carefully built start to crumble.

Fighting her attraction to Jack, Val tries to focus on the case. However, as more bodies appear, she's soon introduced to a whole other underworld.