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.
Struggling with the revelation of their shared pasts, Jace and Clary avoid close contact while working with Magnus to track down warlock Ragnor Fell, who may hold the key to waking up the comatose Jocelyn.
Alec, Jace and Isabelle make a plan to finally get Clary back and stop Jonathan, much to Luke's and Simon's chagrin; Magnus struggles to deal with his father's reappearance; Maia must make a tough decision that could affect the rest of her life.
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.
With his new power, Jonathan wreaks havoc on the Shadow world, targeting institutes around the globe, and Clary must make a great sacrifice in order to hopefully stop him for good. Meanwhile, wedding bells are in the air for one special couple.
As Jonathan grows in power with a new ally by his side, the Shadowhunters and Downworlders must combine their powers, venture to Edom and stop their foes before they destroy the Shadow World. Wedding bells are in the air for one special couple.
With the institute under siege by a greater demon, tensions between shadowhunters and warlocks are higher than ever as Alec tries to remain in control of the situation.