While the interior of the manor appears relatively normal, the main point of interest is a suspicious wardrobe located in a small room by a barred door. This wardrobe has a false back panel which leads to a secret basement.
The basement leads into a series of booby-trapped tunnels that eventually lead to Mercer's office. To get past the flame plate trap room either run across the plates as quickly as possible, or examine each plate before stepping on them. Trap plates will have scorch marks on them in the shape of an "X", while safe plates will be clean.
During the Thieves Guild questline, the manor must be infiltrated to get Mercer's Plans. Entry can be gained by going to the back of the house and speaking to Vald. Engage him in a persuasion test and if successful he will give up the key, which opens the back gate of the manor. Next a ranged spell or shoot an arrow at the gearbox under the balcony and a ramp will fall down. (Or Vald can be killed and the key taken from his corpse, or released from debts as described here)
To avoid conflict with Vald, wait for him to walk in front of the gate and then pickpocket the key from him. This key opens the gate and the second floor door (both expert locks).
- In Mercer's office, in the "hidden" basement, there is a bowl filled with precious gems. These gems will respawn a few days after taking them.
- Chillrend - a unique sword that is in Mercer's office inside an expert display case.
- Bust of the Gray Fox - a unique item depicting the Gray Fox required for the quest The Litany of Larceny.
- Mercer's Plans - a quest item for The Pursuit. It is on the table in Mercer's office.
- The Red Kitchen Reader (Sneak) - on the table with Mercer's plans.
- It is possible to get into the manor without starting "The Pursuit" by jumping onto the roof of the Temple of Mara and then onto the roof of the manor. The expert locked door there can be picked to enter the house. Another way is to use Whirlwind Sprint to get to the manor's balcony from the house next door. The third way is to shoot gears on the platform hinge with an arrow.
- The loot and enemies inside the manor appear to reset almost immediately after being cleared. Therefore the manor could be a source of limitless gold if patient enough to constantly clear and loot it again and again. This occurs even if Mercer has already been killed.
- If you loot the house via glitched entry before "The Pursuit", you cannot turn in Mercer's Plans to Brynjolf.