Pratchett's House is a large apartment located on Kaldwin's Bridge belonging to the aristocrat Pratchett of Pratchett Jellied Eels. The building can be spotted by Corvo Attano when he first enters the section leading to Kaldwin's Bridge during the mission The Royal Physician.
The first floor of the building consists of a hallway and one poorly-lit room, and it contains many valuables that Corvo can sell for coin.
On the second floor is a personal lounge for Pratchett with his chair in front of the fireplace. Here, Corvo can find a book and some elixir, as well as a few sellable items.
The third floor is Pratchett's bedroom. It is here that Corvo can find the source of a humming sound that can be heard from the second floor: a locked safe. Using a note found on this floor, Corvo can figure out the combination for the safe, which is hidden in a series of paintings throughout the house. Inside the safe is a rune and two gold ingots.