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? In this riveting novel from the New York Times bestselling author of The Passenger, every answer raises a new, more chilling question.

Owen Mann is charming, privileged, and chronically dissatisfied. Luna Grey is secretive, cautious, and pragmatic. Despite their differences, they form 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. They're still best friends years later, when Luna finds Owen's wife brutally murdered. The police investigation sheds light on some 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. The Accomplice examines the bonds of shared history, what it costs to break them, and what happens when you start wondering how well you know the one person who truly knows you.