The Slums are adjacent to the Necropolis District. It is an area so poor that the nearby Dandies barely bother to maintain a presence there.
On the edge of the Slums, near the Necropolis, is the Cobblers House, which has a secret entrance to the Necropolis Catacombs in the basement. This entrance is sometimes used by the Spectres to enter the Slums without having to walk the streets. It is a safe bet that Sabrine is aware of the significance of the Cobblers house.