'Criminal Minds' season 12 spoilers: BAU investigates a man who claims to be Dr. Lewis' brother in episode 7

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A promotional photo for season 12 of "Criminal Minds."

This week on "Criminal Minds," Hotch's (Thomas Gibson) fate was finally revealed, and a member of the Behavioral Analysis Unit was promoted as the new chief.

Earlier this year, Gibson was fired from the show after an on-set altercation with writer-producer Virgil Williams. Fans wondered how "Criminal Minds" would handle the star's exit as Hotch had been a member of the BAU since day one.

On Wednesday's episode "Elliott's Pond," Rossi (Joe Mantegna) told the team that Hotch had not been on special assignment like they thought he was. Hotch found out that one of their most infamous Unsubs, Mr. Scratch (Bodhi Elfman), had been stalking his son Jack (Cade Owens), and he had the boy under 24/7 surveillance. However, when Mr. Scratch showed up at Jack's school, Hotch decided that he and his son should go on witness protection, and Rossi said that the BAU can never talk to him again. He also revealed that Hotch has resigned from the team.

With their leader gone, the BAU needed a new chief, and Rossi said that Hotch requested that Prentiss (Paget Brewster) take over. Prentiss was in two minds as she has a life and a boyfriend back in London, but J.J. (A.J. Cook) and Reid (Matthew Gray Gubler) told her that if she didn't accept the promotion, then someone new would have to lead them. Towards the end of the hour, Prentiss accepted the position, and the team had a celebration at the office.

Next week, in the episode titled "Mirror Image," the BAU opens an investigation when a man who fully believes he is Dr. Tara Lewis' (Aisha Tyler) brother arrives in town. The man knows everything about her and her family, and she is unable to make contact with her real sibling.

In the promo for the episode, Tara sits down with the man and asks who he is. The man answers, "Tara it's me — your brother." The man also got to speak with Tara's father, and he said that he wants them to be a family again.

Later, Tara tells Prentiss that whoever the man is, he's good at pretending to be her sibling. It appears that Tara's real brother has been kidnapped, and the BAU immediately takes action to protect one of their own.

"If someone's messing with you, they're messing with all of us," says Rossi.

"Criminal Minds" airs Wednesdays at 9 p.m. ET on CBS.