there is one key (i think when they come out it's the right one) and with it you open the door. then you get a desk, and you open the left drawer. there you'll find a magnifying glass, and if you aim it on a paper on the desk it'll magnify and reveal a riddle. don;t nko how to post a spoiler so the answer is
chapter(s?)
for the rest read my other post 😄