Here's what we know about episode 17.
The CW Press Release
“The British Invasion” — (8:00-9:00 p.m. ET)

THE WINCHESTERS FIND KELLY KLINE – Sam (Jared Padalecki) and Dean (Jensen Ackles) get a lead on Kelly Kline’s (guest star Courtney Ford) whereabouts. Mick (guest star Adam Fergus) drops by the bunker unexpectedly and decides to join the hunt. John Showalter directed the episode written by Eugenie Ross-Leming & Brad Buckner (#1217). Original airdate 4/6/2017.
The original trailer
Inside Supernatural
The NEW Sneak Peek
 The promotional pictures


For  Behind the Scenes pictures from around the web go to the discussion thread for episode 17.
Brad and Eugenie do mytharc! We have a host of returning characters. On the human side we have Mick, Kelly,, Ketch, Mary and Eileen! On the demon side we have Dagon, Crowley and Lucifer. On the combo side Kelly is obviously pregnant and Dagon is still protecting her. Mick gets instructions to either assimilate or eliminate Sam and Dean, who are "out of control". Mick brings in a helper who isn't Ketch. Mick is told to get Sam and Dean to obey or they get turned over to Mr. Ketch, so we are seeing the BMOL becoming antagonists. This looks it should advance this season's story quite a lot on almost all fronts. Cas and heaven are the only parts that seem to be missing. I'm not sure how much Sam and Dean we can have with all these other characters. What clues do you get from all these hints? Are you looking forward to the mytharc being advanced? Are you glad to see Eilleen? I know I am. Share your thoughts in the comments or in the discussion thread for episode 17.
UPDATE: We're getting a nice, sympathetic look at Mick. Does that make it more likely that he will join Sam and Dean? Or more likely that he will die this episode? We've had luck adding good looking guys to the cast already, but this could also be the big farewell to to Mick. Share your thoughts.