The Office of the High Overseer is the principal residence of the High Overseer and a gathering place for Overseers within Dunwall, located in Holger Square. It is the central location of the High Overseer Campbell mission.
The Office of the High Overseer contains all necessary facilities for the functioning of the Abbey of the Everyman in Dunwall. These include a gathering place for worship and collection on the first floor, a room with urns containing the ashes of notable members of the Abbey including those of High Overseers and High Oracles, a kennel for the keeping of wolfhounds, a meeting room, a library, and an interrogation room. On the upper level is a dining room where the High Overseer conducts meetings. In front of the Office in Holger Square are stocks used to punish Overseers for their indiscretions or, presumably, to exact punishment for any crime deemed worthy by the Abbey.
A back area of the Office that contains a back yard and various workshops for the conduction of Abbey business (the destruction of bone charms and runes, the holding of abducted children awaiting The Trials of Aptitude, the creation of Overseer music boxes, propaganda broadcasts, etc.), as well as Overseer quarters, warehouses and kitchens.
On the lower floors of the Office, Thaddeus Campbell maintains a secret room for licentious and sacrilegious activities; various articles of clothing, a note and an audiograph shed light on his sexual and sometimes murderous exploits with courtesans. A rune can also be found on display in a case beside a copy of Litany on the White Cliff.If an alarm is triggered within the building, the Office goes into a 'Lockdown' procedure. All windows will be shuttered, and both Overseers and the City Watch will be on high alert.
- While Campbell's secret room can be seen through a barred window in the Holger Square storm drains, it can only be accessed by pressing the eye of the Holger statue across from the exit to the Kennels.
- The Sokolov painting of Campbell in the process of being painted in the prologue can be found in Campbell's secret room.
- When Corvo Attano first passes by the central gathering area, an Overseer named Sturgess can be heard preaching about the Outsider, and entertaining questions from churchgoers.
- On the second level of the Office of the High Overseer, Corvo can hear two Overseers discussing how one of them was caught on a ledge during a lockdown.
- In the archives, the Overseer's speech changes depending on chaos level. On low chaos he calls Corvo skilled and says that he got out of Coldridge with half the Watch looking for him. On high chaos he says that Corvo is bloody-minded and that he left a trail of bodies. The Overseer finishes his speech by accusing Corvo of practicing black magic.