When Criminal Minds ended Season 12 in May with a car accident cliffhanger, showrunner Erica Messer told TV Guide that she "certainly hope[d]" the whole cast was returning for Season 13. But, she added, "If I've learned anything in all these 13 years it's you can't truly prepare for anything."
A month later — and less than a year after Thomas Gibson was fired after an altercation with a writer-producer — the show, and its fans, were hit with another surprising cast shakeup in its long history of them. While A.J. Cook and Kirsten Vangsness secured raises to return after protracted negotiations, Damon Gupton, who joined the show midway through last season, was let go. A week later, Daniel Henney, who starred on the just-canceled spin-off Criminal Minds: Beyond Borders, joined the mothership, essentially replacing Gupton's Agent Stephen Walker.
"It was difficult," Messer tells TV Guide. "As you know, these decisions aren't made quickly or anything like that. Everything was a thoughtful decision."
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Talk of moving Henney's Agent Matthew Simmons to Criminal Minds began between network and studio executives and Messer not long after Beyond Borders was canceled. "'The discussions were, 'Do you think Daniel would want to join Criminal Minds?' But of course to add one more that means someone's not coming back and that's never an easy thing when someone isn't returning to the show."
Eventually, Messer says, "the decision was made that made that Damon would not be returning and Daniel would be joining, so then it's up to us to tell the stories and have them make sense."
The irony, of course, is that Gupton joined the show at the request of CBS to add an eighth character — making it the largest cast the show's ever had at one time — following Gibson's exit. It's not unlike Rachel Nichols' addition in Season 6 and her subsequent dismissal during the summer hiatus after both Cook and Paget Brewster, who were dropped by CBS, returned for Season 7. "That's never an easy thing to have those conversations with an artist," Messer says. "You never want to have those. And [Gupton is] somebody who is so respected in our family of Criminal Minds."
Worse, since Gupton's first episode was in January and the back half of the season was heavily focused on Reid's (Matthew Gray Gubler) imprisonment, Walker got the short end of the introduction and getting-to-know-you deal, which more than likely played a factor in why he was the one let go. Like they have done with past departures out of their control — Mandy Patinkin abruptly quitting in Season 3, Gibson's exit — Messer says the show will lean into the reality of the situation.
"It did happen. Behind the scenes, we were dealing with, 'Oh, this lovely person just came in and we were so lucky to work with him and it was not long enough, but there they go,'" she says. "And of course, it took about a minute before he was on something else amazing [The CW's upcoming Black Lightning]. But those moments are just crummy."
Walker's exit — he was one of the people in the accident — will be handled in the premiere, which will also see Simmons' full-time arrival to the BAU. Vangsness previously told TV Guide that a "scandal" caused Beyond Borders' globe-trotting IRT to "collapse," and Messer teases that "we are acknowledging that they're not together as a unit anymore."
"Introducing Daniel's character into this world has been a good time," she adds. "Everybody's in love with him behind the scenes, so that makes things much easier. It's lovely. He brings a new energy to the show."
And after so many cast permutations in the past year — Adam Rodriguez also joined last year, while Brewster returned full time — let alone the fact that the show has seen a cast change every year since Season 9, Messer is hoping for some stability. But again, she knows not to expect it.
"We all know anything can happen here," she says with a laugh. "I love everyone here. We're having fun. We're calling it our lucky 13 in the room. Just can't believe we've been so fortunate to have been here for 13 years. We've been through so much. It's crazy."
Season 13 of Criminal Minds premieres Wednesday, Sept. 27 at 10/9c on CBS.
(Full disclosure: TV Guide is owned by CBS.)