Shadowhunters - Season 3, Episode 17: Heavenly Fire
Trailer
After Valentine's death, both of Shadowhunters and Downworlders want to return to their normal, Jace is the only one who know about this wish, Alec presses on Jace to know about what is hidden. Also we see a great demon imposing his control on the institute which make more troubles between shadowhunters and warlocks.