The synopsis for Supernatural season 15 episode 17.
UNITY
 
ONE WAY OR ANOTHER – Dean (Jensen Ackles) hits the road with Jack (Alexander Calvert) who needs to complete a final ritual in the quest to beat Chuck (guest star Rob Benedict). A difference of opinion leaves Sam (Jared Padalecki) and Castiel (Misha Collins) behind looking for answers to questions of their own. Catriona McKenzie directed the episode written by Meredith Glynn (#1517). Original airdate 10/29/2020.

Source:

CW

 
What is the final ritual to stop God? What difference of opinion do Cas and Sam have? What answers will they find? Give us your thoughts in the comments or in the discussion thread for episode 17.