Former FBI agent offers new theory about Nancy Guthrie's disappearance: 'Personal grievance'

A former FBI agent believes that investigators should explore a new possible angle in the mysterious disappearance of Nancy Guthrie.

Jonny Grusing worked in the FBI’s Denver Division for 25 years, investigating violent crimes, missing persons, serial killers and more. He is also the author of "The Devil I Knew: Unmasking a Serial Killer," about the true crime case of Scott Kimball. 

Grusing made it clear that he is only operating off of information that has been made public in the case...