The Behavioral Analysis Unit (BAU) investigates on two unsubs who are possibly operating at the same time in the upcoming episode of "Criminal Minds" season 12.

Titled "In The Dark," next week's episode will explore a murder case that involves two unsubs. According to the official synopsis, the team learns that victims in a new case who are killed in two drastically different ways are dumped in the same city. This leads them to suspect that two unsubs may be murdering their innocent victims at the same time. Also, in the episode, the BAU encounters various challenges as the team tries to make sure that Dr. Spencer Reid (Matthew Gray Gubler) is safe while in prison.

Showrunner Erica Messer recently caught up with TV Line and she hinted that the worst is yet to come for Reid. She shared that the brilliant BAU agent is not completely out of the woods yet. "There are a lot of internal and external factors that are yet to come in that storyline," she teased, "so hang on tight."

Meanwhile, a familiar face will be returning to the show for the May finale. Former cast member Shemar Moore, who played Agent Derek Morgan from 2005 to 2016, has been tapped to guest-star on the show for its final episode. CBS announced the casting in a press release, along with some details on how Moore will cross paths with his old teammates.

"In the episode, Morgan brings the BAU (Behavioral Analysis Unit) a lead in the case against serial killer and escaped convict Mr. Scratch, who has wreaked havoc on the team all season," said the network.

Moore left "Criminal Minds" last year as a series regular and his final episode delivered one of the show's highest ratings ever. Despite his departure, the actor previously said he is not closing his doors on a possible return to the program.

The 12th season of "Criminal Minds" airs every Wednesday at 9 p.m. EDT on CBS.