The Institute is in upheaval after Jace departs with Valentine. Clary, Alec and Isabelle are desperate to find Jace. Jocelyn has a lot to catch up on, now that she's awake.
The downworlders retaliate after Valentine's attacks. The New York institute deals with the repercussions Valentine caused. New faces emerge from the shadows to help the Shadowhunters.
Clary and the team search for the final Mortal Instrument, whilst Isabelle fears Max is growing up too fast. Maia struggles with her feelings for Simon.
After a devastating attack at The Institute, everyone is on high alert as the Shadowhunters close in on their hunt for Jonathan. Meanwhile, Simon and Maia help a new downworlder as the Seelie Queen demands an answer from Magnus and Luke.
Jace and Clary rush to make a final stand, but when a traitor is revealed, they may have a bigger fight on their hands than expected. Meanwhile, Alec and Izzy must fight off a large mass of demons that have unexpectedly shown up.