The first time through the episode, I didn't get what the whole point of that 'clue/evidence' was other than the fact that there is something 'in the walls'. I also thought the 'wrestling' came from fighting with rats or the girls victims or something.

I think it's just me being completely clueless and slow, but I figured out where the 'wrestling' sound came from. I thought it's pretty clever. Enough stalling, I think it's the "wrestling" between the brother and the sister. What'd you guys think it was?