After episode 20's theme focusing on family issues, fans of "Criminal Minds" will get enjoy something different, dark, and scary with episode 21, "Mr. Scratch." The official synopsis states that the Behavorial Analysis Unit will be chasing an UnSub unlike any they have hunted before. 

The synopsis reads that three different people implicated for murder report they were attacked by a mysterious "shadow clawed monster" at the very moment the crime was happening. Now, the BAU speculates that none of the three suspects is the real culprit, indicating there is an UnSub capable of mind-control. 

However, as the team continues to hunt the unknown subject, one of the team members is put in danger. Unfortunately, the promotional trailer and the official synopsis do not state who is in jeopardy or what danger they are facing. It is possible that this mind-controlling UnSub may be an early indication of the criminal the team will face in the finale. 

According to showrunner Erica Messer as she spoke to Entertainment Weekly, the last few episodes of the finale will focus on Jennifer Love Hewitt's character, Kate, who was introduced in the season premiere. 

Messer stated, "By the end of episode 22, we do a mini cliffhanger in that we know that Meg and her best friend are being kidnapped by the guy we saw in the premiere ... The finale is our team fighting for one of our own to get her loved one back." 

This may serve as a bookender for Hewitt's character, closing her participation in the series, or it could open up the door for her character to remain as a series regular in future installments. 

Starting with "Mr.  Scratch," the series may find a compelling reason to give AJ Cook and Hewitt some time off before the inevitable season 11 so that the two of them can deal with their real life pregnancies.

"Criminal Minds" season 10 episode 21 will air on April 22.