When Dee Warner disappeared from her Michigan home, her family launched an exhaustive search. No car. No struggle. No clues. As days turned to weeks, questions—and accusations—took over. What really happened to Dee? Watch "People Magazine Investigates" Monday on ID and stream on HBO Max #PeopleMagazineInvestigates People | Investigation Discovery

Watch the full episode of People Magazine Investigates After Show: The Long Island Serial Killer, available now, on the new People/Entertainment Weekly Network (PEN). Go to http://people.com/pen/ or download the PEN app on your mobile or connected devices. | Investigation Discovery