Article continues below advertisementNearly three months into the investigation, Nancy Guthrie remains missing - and now, a former FBI agent is weighing in with a chilling new theory about what may have happened.During an episode of "Brian Entin Investigates," ex-FBI agent Steve Moore shared his thoughts on the case, including the possibility that more than one person was involved in the suspected kidnapping.Article continues below advertisementSource: @Brian Entin/YoutubeBrian Entin continues to report on the case.