According to the synopsis from Hollywood Hills, "Criminal Minds" season 11 episode 17 will see the Behavioral Analysis Unit (BAU) hunting for an UnSub (unknown subject) responsible for kidnapping children in the dead of night, right while the parents are asleep. 

The episode will be titled "The Sandman," an obvious reference to the mythological creature from European folklore believed to grant people dreams and, in some cases, nightmares. This may be due to the fact that the kidnapper waits for the parents to go to sleep before moving in to take the children.

Unfortunately, the synopsis does not reveal if the team already has some sort of clue regarding the UnSub and it is likely they will need to build an entirely new profile in order to catch him.

While investigating the cases, Derek (Shemar Moore) will try to figure out who was responsible for kidnapping him in the previous episode. In the last episode, Derek was abducted by a group of armed men and was subsequently tortured. He only managed to survive due to the encouraging hallucinations of his father until his team rescued him.

Derek's father, police officer Hank, was portrayed by actor Danny Glover. The character reportedly died when Derek was only 10 years old, which confirms his appearance was only a hallucination. 

Unfortunately, as pointed out in a report from Ecumenical News, neither abduction case will be resolved as episode 17 is only one half of a two-episode story arc. Episode 18, "A Beautiful Disaster," will reportedly tie up the loose ends of the story.

It is also pointed out that the episode will be directed by Joe Mantegna, who plays David Rossi. Episode 18 will then be handled by Matthew Gray Gubler, who plays the brilliant Dr. Spencer Reid. Thomas Gibson, who plays Aaron  Hotchner, was responsible for directing episode 5 and episode 16, making these three episodes entirely run by the cast.

"Criminal Minds" season 11 episode 17 will air this March 16.