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.

With two of the three Mortal Instruments missing, everyone is on the hunt for the last one – The Mortal Mirror. Jace and Clary are on the hunt to recover it first before it could fall into enemy hands. But along the way, Clary realizes that her brother Jonathan may be closer than she thought. Meanwhile, Isabelle has a hard time accepting the fact that her little brother Max is growing up, and Maia struggles to bring her guard down with Simon.

Someone is out to get Simon and Jace is on the hunt to find out who it is, meanwhile Clary turns to Luke to find a way to help Jace. Alec worries about the future of his relationship after learning more about Magnus’ romantic past.