Irene is given a secret task by the Library's upper echelons, kill Alberich, the Library's arch enemy, who has now been revealed as her father. Other librarians lower down the pecking order are told she has gone rogue, so she only has herself, her lover, Kai, (a dragon in human form), and their friend, Vale, the great detective, to rely on. Irene searches for Alberich, and for her own origin story (because the Library is all about stories). If her father is Alberich, who is her mother? She ends up looking for the origin of the Library, as well, and the Library doesn't like that. Everybody's life is on the line as Irene's search reveals more than she wants to know. Se can't unknow things, however, and this is something she has to see through to the bitter end. This is certainly the end to this particular story arc, though looking at Ms Cogman's website she says it may not necessarily be the end of the series, just the end of this season.