The BAU will help Reid (Matthew Gray Gubler) protect his mother on the next episode of "Criminal Minds" season 12.

During the previous episode, Reid's mother Diana (Jane Lynch) decided to visit him in prison. Since she was diagnosed with schizophrenia, she had to come with a nurse to accompany her.

However, Diana fired the nurse that Reid hired for her. Then, she employed a new nurse named Carol, who turned out to be the killer by proxy Lindsey Vaughan (Gia Mantegna).

At first, Reid could not recognize where he first met his mother's new caregiver. But when he heard her voice just before she whisked Diana away after the prison visit, he realized that the new nurse was present during the night when he supposedly killed Nadie Ramos (Ani Sava). He then discovered that she could be the one who framed him for the crime that he did not commit. But his realization came too late, since Lindsey already took away Diana.

In the upcoming episode titled "Green Light," Reid's suspicions turn out to be true since his colleagues confirm the abduction.

The trailer for the episode reveals that BAU chief Emily Prentiss (Paget Brewster) tells the rest of the team that Reid's mom is kidnapped. The news seems to have a major effect on Reid, since he is seen in a highly emotional state in the video.

Prentiss also tells the rest of the BAU team that if they do not succeed in saving Diana, they might lose Reid, too.

Showrunner Erica Messer tells TVLine that the upcoming episode, which also serves as the penultimate installment of the season, will focus mostly on Reid's story. According to Messer, the episode will showcase "a satisfying end to the journey that he has been on" since the middle of the season.

CBS will air the next episode of "Criminal Minds" season 12 tonight, May 3, at 9 p.m. EDT.