In Investigation Discovery's new series Dark Minds, non-fiction crime author M. William Phelps and criminal profiler John Kelly revisit unsolved homicides believed to be the work of serial killers. Joining them in the hunt for answers is an unlikely and anonymous source: a convict serving multiple life sentences for a series of murders. Known only to audiences as "13″, the source offers his "expert opinion" about potential motivations behind these chilling cold cases, using his own personal experience to formulate theories. Featuring crimes that echo the horrors of the infamous Green River Serial Killer, The Hillside Strangler and the BTK Killer, Dark Minds brings fresh eyes to unsolved serial killer investigations using the combined instincts of three unique perspectives.