City of Fallen Angels is the fourth book in the The Mortal Instruments series by Cassandra Clare. The series was meant to end with City of Glass; it was announced in March 2010 that a fourth book would be added, with Cassandra Clare later saying that she views this as a "second trilogy" in the series. The book was released on April 5, 2011.
The book follows Simon's difficult transition into vampirism. Simon receives an offer from a vampire named Camille Belcourt who claims to have been usurped by Raphael. She says that if Simon joins her side as the Daylighter, then he will finally earn his place in vampire society.
Jocelyn and Luke, now engaged, attend an engagement party organized by Luke's werewolf pack, in which Simon disappears. Clary also disappears after being kidnapped by Jace. He lied to Clary about leaving the Silent Brothers early (though Jace does not lie about how he wants to be bound to Clary, as the possession has not affected his feelings for her). Jace tells Clary about a rune that binds them to one another forever. Clary accepts and hands him her stele. He begins to draw a rune, but Clary finds out too late that this is not the rune he told her about. She begins to fall unconscious and Jace catches her and carries her away. Simon is led away from the engagement party by Maureen, now a vampire, and is taken to Lilith, who has been alive since the beginning of time. She turned up at one of Simon's band's gigs and introduced herself as a promoter called Satrina (one of 17 names given to Lilith). She explains that she needs him to resurrect Sebastian (Jonathan) from the dead. When Simon tells Lilith he cannot bring the dead back to life, she tells him that he has had that power since he became a Daylighter. In order to persuade him to resurrect Jonathan (Sebastian), she possesses Jace by a rune and orders him to kidnap Clary. Jace brings Clary to Lilith and she orders him to kill her if Simon does not resurrect Jonathan (Sebastian). Simon reluctantly bites Sebastian and drains some of his blood; being poisoned in the process due to Sebastian's demon blood.