<Username> on 22/4/2019 at 10:16
I think Hector's room is a secret area inside another secret area:
#1: West of the library, there is a small office with a painting of a skull. The book "List of Debts" lies on the table beneath it. Turn around and flip the switch on the lower left of the entrance. This opens a secret area behind a bookshelf on the Northern wall of the library.
#2: In the secret area, you will find a throne room. Look behind the throne: The hidden lock requires the Master's Key. Unlocking it opens the bookshelf in the corridor leading to the throne room. Behind this bookshelf is what I assume to be Hector's room. There is a note from Alexei to Hector on the table.
#3: In the Eastern wall of Hector's room is a locked safe. You can open it by flipping a hidden switch behind the altar on the Southern wall.