We have the synopsis for Supernatural season 13 episode 18.
 
From KSite
 
DANNEEL ACKLES AND RICHARD SPEIGHT JR. RETURN – Lucifer (Mark Pellegrino) rules over heaven but things aren’t going exactly as planned, exasperating his first lady, Jo (guest star Danneel Ackles). Sam (Jared Padalecki) and Castiel (Misha Collins) are perplexed by the return of Gabriel (guest star Richard Speight Jr.). Meanwhile, Dean (Jensen Ackles) gets one step closer to finding Mary and Jack. Amyn Kenderali directed the episode written by Brad Buckner & Eugenie Ross-Leming (#1318). Original airdate 4/12/2018.
 
So, things aren't going according to Lucifer's plan. How will Aneal react? Sam and Cas find Gabriel, how do you think that happens? How does Dean get one step closer to finding Mary and Jack? Give us your thoughts in the comments or in the discussion thread for episode 18.