One young woman realizes how dark the city can really be when she learns the truth about her past.

After getting a clue about who may have wiped Clary's memories, the crew hunts down the High Warlock of Brooklyn, Magnus Bane. With all of the warlocks in hiding from Valentine, the team must lure Magnus out with something he can't refuse - a killer party and something very valuable. But with emotions running high, more may come out of their meeting with Magnus than just the retrieval of Clary's memories.

Meanwhile, Simon doesn't seem to be himself after his recent Downworlder encounter.

Tensions escalate between Alec and Clary as they don't see eye to eye on the best way to hunt down Valentine. But when Jace and Isabelle are sent on an intel mission to the Seelies by Maryse Lightwood, Alec is put in charge of keeping Clary safe, much to both of their chagrin. With his hard-as-nails mother back in town and Clary's rule-breaking tendencies, Alec finds himself struggling to stick to the Claves rules while keeping his promise to Jace.

Meanwhile, the New York City Werewolf pack begins their hunt for Clary and The Mortal Cup.

After piecing together the clues as to where her mother hid the Mortal Cup, Clary, Jace, Alec and Isabelle are on the clock to find its hiding place before anyone else. But with demons and Downworlders lurking everywhere, obtaining the Cup may not be as easy as they had hoped.

Meanwhile, as Simon's symptoms become increasingly worse, he fears he is turning into a vampire.

The hunt is on for Jace Wayland, and Alec and Isabelle hope to reach him before the rest of the Shadowhunters do. With orders from the Clave of “shoot to kill,” the Lightwood siblings must act fast. Also on his own search, Simon turns to Magnus for help when he finds himself at odds with both Raphael and Aldertree. Meanwhile, Clary struggles to find where she belongs since she doesn’t seem to fit into the Shadowhunter world, yet can’t go back to her mundane life.

Already cut off from the Institute and his friends, Jace finds his situation worsen when he becomes a target for the New York wolf pack who believe Jace to be a killer. And don’t forget about Aldertree and the Shadowhunters who continue their own hunt for Jace! With Jace becoming the most wanted man in New York, can his friends get to him before everyone else? Meanwhile, Simon is on a search of his own as Raphael puts pressure on him to find Camille.

To help get answers to what Valentine may be planning, Isabelle and Clary are sent on a mission to visit the Iron Sisters. Once there, more truths may be revealed than Izzy and Clary planned. On a mission of their own, Simon and Maia are determined to find Luke who is still missing after the demon attack at the Institute. Meanwhile, Magnus and Alec finally go on their first date.

Luke’s sister shows up at the Jade Wolf claiming innocence about the recent attack. But with Luke not trusting a word Cleo says, he finds himself at odds with Clary who sees an opportunity to get to Valentine. Yet how far will Clary go to prove she is right about Cleo? Meanwhile, Simon gets dating advice from a surprising source as Isabelle takes a dangerous path.

The New York Institute is under attack as Valentine’s plan for The Soul Sword is getting dangerously close to coming to fruition. The Shadowhunters must act fast to save their loved ones and the rest of the Downworld. Meanwhile, some of the Downworlders have their own plan to stop Valentine and their target is Clary.