The Butler sends us down ahead of him to check the cellar. He gives us a short headstart. We discover the smashed (empty) bottle but nothing else seems amiss. The Butler then is seen sprinting into the room, and it’s clear he was already running before he rounded the corner. He can’t possibly have seen the bottle before he started his mad dash.
He quickly sweeps up the glass shards while very dramatically wailing about how upset Mark would be by the mess, “…if only he were still alive!!”
I think the Butler is giving us a hint twofold:
Mark is still alive, and he’s somewhere in that cellar.
I’m betting there’s a hidden door/passage of some sort in the wine cellar, behind which Mark is being held prisoner. The broken bottle is the Butler’s decoy prop should anyone question why we both went down to the cellar–we heard a crash. He’s howling so loudly as we leave to make sure we get his point, as well as to keep up the appearance of grieving servant, so the killer(s) don’t find out he knows Mark isn’t dead and make him the next target.
A Glitch Named Anti 