Simon and Clary are making out in a canoe in Simon's garage. Jace breaks up the mood. Clary starts feeling pain as a strange marking covers her hand.
Magnus asks Alec to come to him if he ever feels in pain to jump. Magnus determines Clary's marking is a curse caused by Iris's blood oath. Clary must find Madzie or else she will die.
Victor Aldertree asks Isabelle out to dinner, but she turns him down.
A lone werewolf, who is in fact Maia, starts to attack Clary. She defends herself and stops her. Maia defends her actions as Clary's death will save everyone. Everyone departs to find Madzie, but Luke stays behind.
Dot looks after Madzie in Valentine's prison.
Alec confronts Aldertree about how his sister is acting and what he knows. Isabelle, meanwhile, is on a cooking date with Raphael. He reveals that his sister is alive and he cooks for her at the church. Isabelle lets Raphael feed on her.
Maia reveals everyone knows about Clary. Luke traps her a storage room; she panics as she is claustrophobic.
Simon trades Jace's jacket with a homeless man to get Madzie's scarf. The scarf will help them track her location. Clary asks Simon to promise if Valentine gets to her, he will elminate her. He refuses, but Jace takes the deal.
A small group of Downworlders, which includes Raphael, Magnus and Luke, come together to figure out what to do about Clary. The Seely pitches they kill Clary to save all.
Maia panics while trapped in the storage room. She succumbs to her instinct and transforms into the wolf; she tears everything apart.
Clary's curse affects her body harshly. Simon comforts her and the two embrace each other.
Magnus reveals to Alec what he learned at the meeting about Isabelle and her addition to vampire venom. Alec demands Magnus bring him to where Isabelle is.
Jace finds Valentine and Madzie in a shop. He forces Valentine to choose an ultimatum whether to let Clary and Jace die or save them.
Alec breaks up Raphael and Isabelle together during a feeding session. Raphael admits his feelings to Isabelle. Alec blames Magnus for not telling him sooner about Isabelle and the venom. Magnus demands Raphael get clean before deciding on his feelings for Isabelle.
Jace arrives just in time with Madzie to cure Clary of the blood oath. She opens a portal and forces Clary through it. She's held captive within Valentine's prison.
Simon and Jace spot Downworlders killing a Mundane. Back at the Institute, Alec is getting reports of several attacks as well. Luke, Simon and Jace stop a few of Valentine's mutated Downworlders and demand one show them Valentine's location.
Alec confronts Aldertree about him about what he did to Isabelle. He takes control of the Institute and sends all Shadowhunters on alert to find her.
Jace frees Clary, but Valentine captures Simon. He kidnaps him and they escape through a portal.