The Labyrinth Index is the ninth book in the Laundry Files series, and was released on 30 October 2018. Mhari Murphy is the protagonist. She has been elevated to the House of Lords (taking the title "Baroness Karnstein") and serves under the new Prime Minister following the Laundry-engineered overthrow of the Government described in the previous book. The new Prime Minister Fabian Everyman (an alias of Nyarlathotep) sends Mhari to the United States on a mission to discover what has happened to the now-missing President and who is running America in his stead.