Criminal Minds Criminal Minds

On Wednesday's episode of Criminal Minds, the members of Behavioral Analysis Unit — and viewers — will say goodbye to Agent Jennifer Jareau.

JJ's exit comes after CBS abruptly let A.J. Cook go for creative reasons during the break between seasons.

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And while the plan is ultimately to bring in a new team member, don't look for it anytime soon. "The team has a choice to replace her or not. That's one of the surprises that people don't know about," Mirren says. "Our family has lost a member, and they're irreplaceable. But also somebody has to do that job [as communications liaison]."

"Even if they were to bring somebody else on in the future, the space left by her character is obviously never going to be filled," Gibson adds. "We miss her a lot, and we were lucky to have the time with her when we did."

Criminal Mind airs Wednesdays at 9/8c on CBS.