Derek’s trapped in his mind, where he keeps seeing his dead family - over and over - as Kate manipulates his body in the real world to do her bidding. Deaton finds a way to insert Stiles into Derek’s subconscious to try and wake him from his never ending nightmare.
"You need to come back now, Derek."
"Because I, we need you."
"Jealous" snippet from On Air With Ryan Seacrest [9/4]