A wealthy pharmaceutical CEO's girlfriend is found dead: naked, bound hand and foot, hanging from a balcony. Days earlier, his six-year-old son suffered a mysterious fall in the same mansion. The sheriff says suicide. Her family says murder. A jury awarded them $5.2 million. Then everything changed.

This is the Rebecca Zahau case, and it's one of the strangest death investigations you'll ever hear. We've got deleted voicemails, four separate head injuries that may or may not make sense, a cryptic message painted on a door, and medical examiners who can't agree on what killed her. Police demonstrated that yes, technically, she could have tied her own hands behind her back before hanging herself. But should we believe she actually did?

Fifteen years later, the questions remain: What happened to six-year-old Max Shacknai? What w ...