We have the synopsis for episode 19 of Supernatural season 13.
 
SUPERNATURAL
“Funeralia” — (8:00-9:00 p.m. ET) (Content Rating TBD) (HDTV)


ANGELS, WITCHES AND REAPERS, OH MY – Sam (Jared Padalecki) and Dean (Jensen Ackles) must stop Rowena (guest star Ruth Connell), who is on a deadly mission. Meanwhile, Castiel (Misha Collins) looks to heaven to recruit angels for an impending invasion but is shocked by not only what he finds, but who. Nina Lopez-Corrado directed the episode written by Steve Yockey (#1319). Original airdate 4/19/2018.

Source:

The CW

 
 Rowena returns! Is her deadly mission to kill Lucifer? Does Cas finally find out that Lucifer has taken over heaven? If so, has he not been listening to "Angel Radio"? Or is Lucifer just shy about tooting his own horn? Give us your thoughts in the comments or in the discussion thread for episode 19.