June 01, 2022
There is a chest in Treasure of Nadia in the attic above the Full Mast Bar. To open the chest you need a key - the Attic Key. Unfortunately, this key is not very easy to find.
The Attic Key appears relatively early in the story as a blue marker on the ground in Estero Park. Unfortunately, you can not distinguish it from a talisman. When I played the game, the blue marker appeared at the very southeast of Estero Park at the entrance to the cave. However, I am not sure if this is always the case. Also, I assume you need to own the Metal Detector to make it appear.
Once you have the key to the attic, you can open the chest above the Full Mast Bar. Inside the chest, you will find a dartboard, which you can use to decorate Henry's house.