When I Cannot Sleep

There are tales and tales of mysterious doors that yield to well-hidden keys. Surely, then, there is at least one tale of the opposite occurrence. An adventure, in turn, ensues for that single solution: that one door, that one key. What then if only the knowledge of both door and key exist, leaving but two solutions to be sought?

What awaits behind both door and key that is worth the trouble of a search? Can anyone tell me that?

EDIT: Spoke to John. Somewhat comforted. Somewhat not.