The Zombie Apocalypse

You drive uptown to your folks. You see their house has been raided! You hop out. Run inside. "Mom! Dad!" You yell. "Mmmph! Mmmmmmph!" You run to the back closet in the small, truck-delivered house. You hear bangs from the attic door. You quickly pull the ladder down and climb up. You see one of the worst sights you have ever seen. No, it isn't dead corpses. No, it isn't parents becoming dead corpses. It is a note. It reads,

'If you ever want to see your parents again, I will give you a clue. Crawl Space.'

The ink is from a quill. You can tell because it is beside the note. The ink rubs off. It is fresh! You have to go save them.