A gripping psychological thriller on the bonds of friendship and the cost of breaking them, from the New York Times bestselling author of The Passenger and the Spellman Files.

Everyone has the same questions about best friends Owen and Luna: What binds them together so tightly? Why weren't they ever a couple? And why do people around them keep turning up dead?

Owen Mann is charming, privileged and chronically dissatisfied. Luna Grey is secretive, cautious and pragmatic. Despite their differences, they begin forming a bond the moment they meet in college. Their names soon become indivisible—Owen and Luna, Luna and Owen—and stay that way even after an unexplained death rocks their social circle.

Years later, they're still best friends when Luna finds Owen's wife brutally murdered. The police investigation sheds some light on long-hidden secrets, but it can't penetrate the wall of mystery that surrounds Owen. To get to the heart of what happened and why, Luna has to dig up the one secret she's spent her whole life burying.