We have the synopsis for Supernatural episode 5!
 
SUPERNATURAL 13.05 “Advanced Thanatology”: While working on a case involving the ghost of a demented doctor, Sam (Jared Padalecki) and Dean (Jensen Ackles) get assistance from an unexpected source – Billie (guest star Lisa Berry). Castiel (Misha Collins) finds his way back to the Winchesters. John Showalter directed the episode written by Steve Yockey (#1305).
 
Okay, I knew Cas was coming back and episode 5 sounds about right. I never thought Billie would return, but I am so happy she is! Are you glad Billie is alive? How do you think she survived? Did she fake her death? Could it be that the big guy, Death, is still alive? Are you glad to see Cas return to the main universe and reunite with Sam and Dean? Let us know in the comments or in the discussion thread for episode 5.