Former Illinois cop Drew Peterson is still behind bars for the murder of his third wife, but his 4th wife Stacy Peterson is still missing. The mystery is the focus of the newest episode of Nancy Grace's A&E show “Grace vs. Abrams” and this episode. Nancy digs into the case with Drew Peterson's former lawyer Joel Brodsky, Cold Case Research Institute director Sheryl McCollum, psychologist Dr. Chloe Carmichael, and reporter Robyn Walensky. Grace also updates the Penn State frat hazing case with lawyer Troy Slaten, prosecutor Wendy Patrick, forensics expert Joseph Scott Morgan, psychologist Dr. Tiffany Sanders and reporter John Lemley.