You never know what you might find.

Kerri and Jason Brown discovered a secret room behind a bookcase containing a homeowner’s worst nightmare – mold. Also in the room was a handwritten note: “You found it!” What the Browns found was a mold problem so serious the previous owner was forced to move, according to the note.
…
“Hello. If you’re reading this, then you found the secret room. I owned this house for a short while and it was discovered to have a serious mold problem. One that actually made my children very sick to the point that we had to move out,” Kerri Brown read from the letter.

Not to make light of this clearly troubling situation, but – wow.

Update 05 November 2007: There’s a lot more to the story.