'Criminal Minds' season 12 spoilers, plot news: Thomas Gibson speaks on show's success and Shemar Moore's exit; Will Reid get along well with Derek's replacement?

The BAU team will continue to move forward after one of their own decided to leave for good, but a new agent will fill the void left by Derek Morgan (Shemar Moore) in "Criminal Minds" season 12.

"Criminal Minds" season 12 promotional image | Criminal Minds/Facebook

Among the BAU agents, Spencer Reid is the closest one to Derek which makes it understandable that he will have a difficult time coping with his good friend's departure. In an interview with TV Guide, showrunner Erica Messer stressed that they will focus on his road to recovery. Messer discussed that losing a co-worker and a friend is never easy, and it will greatly affect an individual's life. Even if Derek is just a phone call away, it will be interesting to see how Reid navigates the workplace now that his closest friend is no longer there. Adam Rodriguez has been recently confirmed as a series regular for season 12, and his character will replace Derek in the team.

Meanwhile, Hotch's portrayer, Thomas Gibson recently caught up with The National to give some insights on the show's success. "... It is crazy that here we are, 11 years on, with a show that found its legs and an audience," Gibson said. "We found a way to tell compelling stories, basically. Criminal Minds looks at what happened in a bad person's life to make them capable of doing unspeakable things to other people. I think the question of why they are compelled to do them – when it doesn't occur to most other people – is really interesting."

After seeing a lot of cast changes over the years, Gibson also gave his take on Moore's exit. The actor explained that it is difficult to say farewell to colleagues, but at the end of the day, it is an opportunity for the crime drama to refresh itself. With the show moving towards its 12th year, fans may be wondering how long will the story evolve. "Well, we still haven't ­exhausted all of the crazy ways in which people are horrible to each other," Gibson said.

Catch the season 12 premiere of "Criminal Minds" which airs on Sept. 28, Wednesday at 9 p.m. ET on CBS.