These chapters represent experiments with characters and dialogue, and they may or may not make it to the final draft of the novel

Daughter of Candlelight – a prelude to the series, where Mia, a high ranking but secret church official, can see demons in the Vatican
The Child in the North – an experimental chapter that plays with all the characters as they work on an exorcism of the son of an infamous Filipino politician
Gatekeeper of the Borders – a characterization chapter that shows how John, who can see ghosts, witnesses the events of The Towers on the Planes later on.
Illuminator of Souls – a characterization chapter that shows how Syl, who can photograph entities, witnesses the events of the Towers on the Planes later on.
Jorge – a backstory chapter for Jorge, later to be the Pope
Matteo – a backstory chapter for Matteo, a priest who can see angels
The Hidden Nine Hours – an experimental chapter that brings some members of the team together with the Pope as he visits the Philippines
The Towers on the Planes – the chapter that sets the research project in motion
The Long Drive Home – the chapter that follows the events of the Towers on the Planes