Chris Marker is a boy originally from Rowhurst and came to the Natural History Museum with Justin and Brooke. He calls himself "The Librarian", and is writing a book known as "The Chronicles of Survival" about the lives of the kids who survived the initial outbreak and how they have been living. He sees books as the future and likes to lose himself to them. He is likely schizophrenic, seeing the ghosts of past friends and writers around him.
Chris Marker was one of the boys on the bus, his nose buried in a book. Chris remarks to himself that books could open doors to different universes and were more interesting than reality, despite sickos being rampant in the streets.
Once at the Imperial War Museum, Chris finds its library and immerses himself into their books, where he finds in the dark, a grey lady. He is likely schizophrenic, but is not negatively impacted by his hallucinations; he finds comfort in the ghost's presence, protecting the books so that she will protect him.
Later in the book when all must evacuate due to the fire spreading across London, Chris is the one to suggest taking the books from the Imperial War Museum and loading it onto the Tesco truck for later information. At the time, others on the truck found it silly to rescue books when in danger of the fire, but Ed agrees that it is a good idea; once Chris collects the books, the grey lady's ghost from inside the library travels with him.
In The Fallen, Chris is in charge of the library when Justin is in charge of the Natural History Museum. Chris holds interviews with all the survivors that come and write down their stories in The Chronicles of Survival, to keep a record and to hold their stories for those in the future.
In The End, Chris Marker writes down the names of all the fallen, honouring their dead.
Justin - Justin is in charge of the Natural History Museum, and trusts Chris to run the library for him.
Lettis Slingsbury - Lettis is one of Chris' "scribes" who he remarks in The End used to be one of his most devoted writers, before the Promithios mission incident.