Being the final season of the series, "Bones" season 12 is expected to answer all the questions left by the previous season. It can be recalled that season 11 ended with some major cliffhangers, the biggest of which was Brennan being kidnapped by a serial killer.

Spoilers for the upcoming season suggest that Zack might be the one to save Brennan from the killer. According to reports, season 11 will further explore his storyline as he becomes the biggest challenge to Booth, Brennan and the whole squad.

In a recent interview, "Bones" executive producer Jonathan Collier teased that Zack will put both Booth and Brennan in jeopardy as he places them in seemingly irreconcilable viewpoints. However, he assured fans that the marriage of the couple will remain strong despite the challenges.

According to showrunner Michael Peterson, fans of the series will get to understand where Zack came from as the series digs deeper into his life. It was previously revealed that Zack could not be the dreadful serial killer, and that he was just a protégé with some mental and psychological disorder. Previous reports claimed that he will change his mind about killing Brennan, but it is also possible for him to die in the process.

In other news, Brennan's ex-boyfriend Sully is set to return to the series as he seeks to deal with an unfinished business with Brennan. His return might be another big challenge for Brennan and Booth's marriage.

"Bones" season 12 will consist of just 12 episodes and is expected to air sometime in January 2017 on FOX.