Reid (Matthew Gray Gubler) has been keeping his incarceration a secret from his mother, but the truth is about to come out.

On Wednesday's Criminal Minds, Diana (Jane Lynch) visits her son in prison, where she slowly comes to the realization that her son is behind bars — and it's because of his trip to Mexico to get her meds for her Alzheimer's. "This is all my fault," she says in our exclusive sneak peek.

"It's that blessing and curse of her condition: Does she really comprehend what's happening?" showrunner and executive producer Erica Messer tells TVGuide.com. "You'll see the side effects of her disease. She does put it together that 'you were in Mexico to help me and the only reason you went back there was because I threw away the medicine you got for me.' There's some guilt associated with her. But there is that part where you wonder if five minutes later she's forgotten about it. It's kind of heartbreaking."

Matthew Gray Gubler and Jane Lynch, Criminal MindsMatthew Gray Gubler and Jane Lynch, Criminal Minds



Diana's visit will provide a major break in the case, likely triggering Reid's foggy memory of that ill-fated day in the motel. Messer says Reid will remember the identity of the the woman who drugged him by the end of the episode. It's an old face, but you can rule out one person already.

"It isn't Cat Adams (Aubrey Plaza)," Messer says. " [The person] is a huge turning point for the story. We kind of put all these crazy pieces together and what we thought was correct. We were missing pieces and now pieces are starting to get filled in. And all of that will add up to Reid's exoneration, fingers crossed, by the time we hit the finale. But there's unexpected trouble that arrives because of all of that."

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

(Full disclosure: TVGuide.com is owned by CBS.)