Scott and Derek seek out an unlikely ally. 

Boyd tries to attack to little kids.

Lydia finds a dead body in the lifeguard chair by an unknown pool.

Scott turns to Mr. Argent for help in tracking Boyd and Cora.

Melissa shows Stiles the body Lydia found and another weren't killed by werewolves.

Stiles thinks he knows what's going on.

Boyd and Cora are trapped in the school boiler room.

Stiles realizes the murders are human sacrifices of virgins.