You already know "What's in the box?" Well, the Criminal Minds equivalent is "What's under the sink?" OK, no one cry-whines it like Brad Pitt did in Seven, but that's what they're thinking.

Wednesday's episode, which is directed by Matthew Gray Gubler, finds the BAU investigating the case of three kids who vanished from a bike path, a mystery that mirrors the disappearance of three children from the same path 30 years ago. Is it the same unsub? A copycat? The cold case will have to be reopened for our guys find out.

In our exclusive sneak peek, the team enters a home, where Prentiss (Paget Brewster) discovers the creepiest makeshift Christmas tree ever — decorated with clothespins, rags, bandanas, Hula hoops and aged Polaroids of the original missing kids. (Poor guys.)

Criminal Minds: Take a tour of the killer prop room

But none of them is prepared to find out what's lurking underneath the sink. (Hint: It's alive.)

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

(Full disclosure: is owned by CBS.)