Simon, Clary, and Jace carry an injured Luke to Magnus' lair. They put him on the couch. Luke is delirious and has hallucinations about Jocelyn who tells him that Clary has the key to finding the Cup, all he has to do is unlock it within her.
Luke frantically starts talking to Clary, but the alpha poison is taking over. Magnus gets some stuff together to make a potion.
At the Institute Izzy tells her mom what she learned from Meliorn. Maryse isn't impressed, and let's her know she doesn't approve of her Seelie relationship.
Luke has calmed down. Simon comforts Clary. Clary feels guilty about all the damage she has caused to people.
Magnus begins working on a potion, but he doesn't have everything he needs, so he sends Simon and Jace out to get the ingredients. Neither are happy about having to work together. Clary looks exasperated at their behavior. Magnus also tells Jace to call Alec, because he needs Alec.
Alec and Izzy are talking about Jace. Alec is still angry with him. Their dad, Robert and brother, Max walk in. Robert tells Alec that he is not happy they have been going on rogue missions with Clary. He wants Clary back at the Institute where she will be safe.
Jace calls Alec and tells him that Magnus requested his presence. Alec isn't going to cooperate because shadowhunters are not supposed to be interfering in downworlder business and this would be interfering with downworlder business.
While Magnus is mixing the potion, he and Clary talk. She vents about her mom and Valentine.
Luke calls out. He wants Magnus to tell Clary everything. Magnus throws some magic on him, but the poison is spreading.
Simon and Jace are having a pissing contest about Clary. Its obvious they don't like each other. Each time Simon mentions Alec, Jace gets angry, and pushes him around. Simon fights back, his vampire abilities glowing briefly, and puts a knife to Jace's throat. It doesn't last long as Jace overomes Simon. He then asks him about what happened at Hotel DuMort.
Alec talks to his mother. Her mother talks about how the Lightwoods have lost the favor of the Clave.
Magnus starts to tell Clary stories about her parents when they were younger, about Valentine and Jocelyn's relationship. He tells Clary how Valentine wanted to rid the shadowhunters of impure blood and get rid of demons.
Izzy overhears her mom and dad talking and tries to find out what the discussion was about to no avail. Her dad gives her a book. It's a cookbook. Her dad tells her that if the Seelie's change sides, they have no hope of beating Valentine.
Clary talks about the downworlders and how she doesn't understand why her father hated them so much.
Magnus tells her that the Clave didn't think Valentine was a threat. He tells her about the Uprising and how he massacred people and took the Cup. Clary is upset about the stories she's being told.
A flashback tells the story of how Luke and Valentine fought and as Valentine was going to kill Luke, Jocelyn comes to the rescue by throwing a knife in Valentine's back. She runs down and they have a sword fight. She gets the cup and runs off.
While Magnus talks, Clary draws. He tells Clary that Jocelyn gave up shadowhunting to protect Clary.
Luke is stirring. Magnus works some magic to hold Luke down.
Izzy tells Alec that his parents are going to marry him off. He walks away saying he's not going to follow the rules anymore.
Jack and Simon are still walking and still having a pissing contest. Jace tells Simon that he has no chance with Chloe. Simon doesn't even know how to respond to this. They arrive at their destination. Jace makes him stay behind. When Jace is gone, Simon hears somehing and sees Camille. He goes running after her, but then come across his own dead body. Before he has a chance to digest this, Jace comes out of the pharmacy and tells Simon to run. A scorpion comes out looking to hurt someone.
Magnus is working his magic to try to control the changes happening in Luke. Alec shows up and Magnus asks him for his strength. Alec agrees and they join hands to make the magic stronger.
Jace and Simon return and give Clary the final pieces for the potion. Clary gives it to Luke and he is immediately restored to his old self.
Izzy and Maryse are arguing about Alec.
Alec and Clary talk. She thanks him for coming and helping. Jace walks in and he and Alec make up. They are friends again. Jace and Clary share a moment when Simon walks in. He's clearly not happy and Jace is smug.
Clary leaves. Simon and Jace just stare at each other. Simon tells Jace he is leaving. Jace is about to say something and Simon leaves a $20 bill for him.
Izzy is playing games with Max when her mom walks in. She asks Max to leave then apologizes to Izzy for being so mean. She shares some information about her past, like the fact that she actually broke the rules when she was Izzy's age.
Luke thanks Magnus then Magnus leaves so Clary and Lukke can talk. She wants to know what they never said anything. Luke then shares the story of how Valentine became evil. It was because Luke and clary fell in love and Valentine was jealous and obsessed with winning Jocelyn back that he started to do crazy things like experiment with demon blood.
Luke had admired Valentine. They were parabatai, but Valentine crossed him by leading him on a mission only to lock him up with werewolves. This is how Lue became a werewolf.
Valentine wanted to use the Cup to make more shadowhunters, but it was forbidden. The demons were winning.
Luke went to confront Valentine and Jocelyn interfered before Valentine could kill Luke. Jocelyn and Valentine fight and Jocelyn takes the Cup and runs. Valentine chases after her.
Izzy has decided she's going to do something about the Lighwood's smeared name. She has transformed from trampuy to sophisticated. She pulls her hair back in a ponytail like her mother's. In fact, she's looking a lot like her mother.
Magnus and Alec have a moment. It's very sweet and might be leading somewhere, but then Alec gets a call from his mother. He has to go, but agrees to have one more drink with Magnus. They talk and Magnus tells Alec that he is attracted to him. He tells Alec that he lied about needing him. He just wanted to see him again. Alec doesn't know what to say.
Clary brings the box out that they pulled from the loft. She asks Luke about it and the initials, J.C. Luke is hesitant, but tells her that was his brother, Jonathan Christopher who died in a fire set by Valentine. Clary put the box down on a blank piece of paper and it disappeared into the paper. She questions Luke about it and he says it's an angelic attribute. Then she remembers when it happened at the coffee shop with the biscotti.
In an instant, Clary realizes she knows where her mother hid the cup.