In the new series “DARK MINDS” on Investigation Discovery, true crime writer M. William Phelps and criminal profiler John Kelly delve into unsolved murder cases suspected to be the handiwork of serial killers. Assisting them in their quest for answers is an unexpected and anonymous informant: a prisoner serving multiple life terms for a string of murders. Known to viewers only as “13,” this source provides his “expert opinion” on the possible motives behind these haunting cold cases, drawing from his own experiences to develop theories. The series examines crimes reminiscent of those committed by notorious figures like the Green River Killer, The Hillside Strangler, and the BTK Killer. “DARK MINDS” offers a fresh perspective on unsolved serial killer cases by combining the insights of these three distinct viewpoints.