“Don’t be silly,” Bob, said Mo, “everyone knows vampires don’t exist!” Thus opens The Rhesus Chart. We quickly come to realize that vampires do exist and we come to wonder why everyone in the Laundry is so dogmatically sure that they don’t. One of the nest of baby vampires that sets the plot in motion is Bob’s toxic ex-girlfriend, Mhari, who manages to convince the Laundry that they should recruit her clutch rather than exterminate them. But there are old vampires who have the Laundry’s newest recruits in their sights.
Sequel to The Apocalypse Codex. More at Charlie Stross’s Crib Sheet and the Laundry Files Wiki.