Nine months after Nancy Guthrie vanished from her Tucson, Arizona, home, a retired homicide detective is offering a bold new theory that there may be more than one person involved in her kidnapping. Chris McDonough, host of "The Interview Room" and a former homicide detective, shared his assessment in an interview with Ashleigh Banfield for NewsNation.

"I'm not convinced of that personally yet, but he could be," McDonough said. "Or, it could be a second person.

I do believe there's more than one. I think there are two involved in this."

When Banfield asked whether he meant "the brains and the brawn," McDonough suggested the dynamic could resemble a murder-for-hire arrangement. He compared similarities of Nancy Guthrie's abduction with a case in which a wife hired six Marines to kill her husband, noting it's "not uncommon for somebody to say, Hey, here's what you'll get out of the situation."

Nancy Guthrie was last seen at her Catalina Foothills home on the evening of January 31. Her family reported her missing on February 1, but no suspect has been named by law enforcement authorities so far.

The family has offered a $1 million reward for any credible information leading to an arrest and recovery. Investigators continue to appeal to the public for tips as the search enters a critical new phase.

Authorities urge anyone with relevant information to contact local law enforcement agencies immediately.