Where is the key to the basement door?

Hint 1 of 14:

Gee, keys are pretty difficult to come by in this game, aren't they?

Hint 2 of 14:

I would imagine that Xaver has them in the drawer of the front desk.

Hint 3 of 14:

Did you ask him about the locked door?

Hint 4 of 14:

He's less cooperative than Gerde.