We begin with a ritual, one that summons a scary demon from another realm. And we mean scary—we're talking about the fear demon, Agramon. And who has summoned him? Why our Big Bad voodoo Daddy, Valentine, who's still lurking around searching for ways to wreak havoc.
Elsewhere in Manhattan, Jace, Alec, and Isabelle are blowing off steam by blowing the limbs off demons. They return home, to the Institute, and learn that their mother, Maryse, has returned from Alicante, where she was during the whole first book. She's mad at Jace, and she didn't even bring them any presents. Not even a lousy snow globe.
Maryse tells Jace that she believes he's been working for Valentine this whole time. She wants him to swear that he hasn't, and that he hates his father. Jace won't do it. Since his family's trust in him is broken, he runs away. He ends up in a dive bar with a bone to pick with a bunch of angry werewolves.
While all this is going on, Clary and Simon are playing house at Simon's house, even though whenever Simon kisses Clary, she's thinking of Jace. Her lukewarm make out sesh is interrupted when Luke calls. He has Jace in his office (Luke seems to be the head of the werewolf pack Jace is scrapping with), and he thinks Clary can talk some sense into him. She heads to the bar, and once Jace is calmed down, he returns to the Institute.
Bad idea. Maryse has called the Inquisitor, who plans on using her handy dandy Soul-Sword to see if Jace is telling the truth. Until this trial by blade, she's going to lock Jace up in prison at the bottom of the Silent City. Good thing he isn't afraid of the dark.
Isabelle calls Clary to tell her that Jace in jail. Once again, Clary rushes to find him. By the time Clary, Alec, and Isabelle reach the jail, Valentine and his pet fear demon have already killed everyone there and stolen the sword! Luckily Jace has been spared. But what's Valentine's plan? Why does he want the sword?
Magnus Bane does some research and decides that Valentine must want to perform the… dramatic pause… Ritual of Infernal Conversion. Dum dum dummm. This will make the Soul-Sword evil, allowing Valentine to summon demons, which he can then control with the Mortal Cup. In other words, this is Very Bad News.
At this time, the Faerie Queen contacts Isabelle saying she wants to see them. They all tromp down to Faerie world, where she tricks Jace into kissing Clary (the steamiest brother/sister kiss since Star Wars) and tells them they each have special powers… but she won't get more specific.
Betrayed by this kiss, Simon runs away to the vampire hotel, where he's promptly devoured by vampires. Oops. Because he ingested some vampire blood last book, this means he will be reborn as a vampire. Clary buries Simon at the Jewish cemetery and he wakes up thirsty for blood.
Soon, pretty much everyone is attacked by demons at some point, and between fighting off these hellspawn, Clary discovers what her power is: she can create new runes. How about a No Demon Rune, Clary? Instead, she creates a Fearless Rune, which makes people Fearless.
Valentine captures Simon and Maia, a werewolf girl, to complete his ritual. Unfortunately, Jace has been re-imprisoned by the Inquisitor, who plans on trading Jace to Valentine for the Mortal Instruments. If Valentine doesn't fork over the Mortal Instruments, she'll kill Jace. Jace tries to tell her this is a stupid idea, because Valentine will choose the Mortal Instruments over him, but she's too blinded by rage (she thinks Valentine is responsible for the death of her son) to listen.
Alec helps Jace break out by telling him that maybe his superpower is to do whatever he damn well pleases. Jace is good at that, so he just jumps right out of the cage, gathers some weapons, and jumps out the window of the Institute just as Clary coincidentally happens to be driving by with Luke.
By this point, everyone finally realizes that Valentine is the main enemy and they all need to stop bickering with one another. Forces united, they storm Valentine's boat. Clary paints the Fearless Rune on Jace and then, of course, gets captured by a demon and dropped right into Valentine's lair. There, she learns from Maia that Simon has been killed. Again. Tough break, kid.
Jace reaches the boat, defeats the Fear demon (the Fearless Rune basically being scissors to the Fear Demon's paper) finds Simon's body, and lets Simon feed off him, bringing him back to life. Together, Jace and Simon find Clary and go after Valentine.
Clary uses her super-duper Open Rune that opens the boat right up and it sinks like a lead weight. In the Epilogue, we find out that vampire Simon + Jace's magical angel blood = immune to sunlight. Jace finally tells Clary that they shouldn't be bumpin' and grindin' because they're siblings, and a mysterious stranger appears on the book's final page to tell Clary that her mother is in a magical coma… but she knows how to wake her!
Look like it's full-speed ahead, next stop, City of Glass.