How to get the last key of Elf 3?

In Mill Elf 3, the last way to get the key is to lock the treasure chest and lock the dangerous building on the first floor. There is a bridge on the left, where there are two water ghosts. After killing the water ghost, you will find a corpse and pull out a key from it.

Then go to the box next to the water and open it. There is a military order in the open box. After reading it, you can go back to the ground and open the box to get the key.

Game plot

After Geralt regained his memory, he began to look around for traces of Ye Naifa. Finally, Yenefa contacted Geralt, whom he hadn't seen for many years, and asked Geralt to meet him in Willoughby village. However, when Geralt arrived at the designated place, the whole village had been razed to the ground by the army, and Yenifa had disappeared. On the way, Geralt met Vesemir, and with his help, he tracked the trail of Ye Naifa together.

On the way, Geralt dreamed of what happened to Kyle Mohan. This dream warned Geralt that his adopted daughter Healy had some problems.

Geralt and his party lived in the White Orchard, and Yenefa appeared in the White Orchard Hotel, surrounded by soldiers from Nevergard. Before catching up with the old lovers, Yenefa insisted that Geralt go to Vijima with her as soon as possible to meet the emperor Nevergard.