Hi,
I highly doubt that nahar is hiding a person in that room. because, even if it was a mentally disabled person, it is not enough to just go and see that person at night. that person will need food and ppl will require more frequent visits during the day. also, if it was a person, how come there's no sound? I don't think it's a person. I think nahar is part of some sort of a top secret mission, and that huge key is I think a key to a locker of some sort. I dont think the secret of his bua has anything to do with the room because that secret is already out.
this is what i think.