Zack (Eric Millegan) may not be the serial killer that the FBI is looking for in the upcoming final season of "Bones."

Fans of the long-running FOX series are counting the days until the season premiere in January. As per CarterMatt, the show will pick up the night Brennan (Emily Deschanel) disappeared. She was kidnapped by Zack, her former intern. That time, the joint forces of the FBI and the Jeffersonian were hard at work investigating the serial killer, the Puppeteer. When Brennan was abducted, the others naturally assumed that Zack was the criminal.

New details reveal, however, that he may not be the bad guy.

As per Buddy TV, the promo photos reveal the whereabouts of Brennan after her abduction. Zack appears to have brought her to an abandoned warehouse. In one of the photos, they are talking seriously. Brennan is in no way trussed up or hurt. Zack looks like he has no plans to cause her harm. What is troubling is that in one of the snaps, Zack is holding a syringe. It looks like it contains poison. Brennan is shown holding her hands up, as if telling Zack to calm down and stop whatever he is planning.

This is the part where Booth (David Boreanaz) finally finds his wife. His photo shows he will shoot Zack if the other man so much as wiggles his eyebrows. Surprisingly, Brennan appears to be defending Zack in the next picture. Her posture suggests that she is asking Booth not to shoot. This is a tricky scene, as Zack's motives will finally be revealed. If he did not kidnap Brennan to kill her, why did he then? If he is not the Puppeteer, then who is? As it is, Booth needs to calm down and listen to his wife. If he pulls the trigger and kills Zack, the mystery will never be cleared.

The last season of "Bones" will premiere on Jan. 3, 2017, 9 p.m. EST on Fox.