So we ran into a bug with this scenario where the end monster didn't spawn. It was 2 player. The map was the one that included Hallway Tile 5 (seem to get that map a lot). We didn't explore the two tiles North of the Bedroom (I believe it was the Greenhouse and Root Cellar) but had entry to the Generator room trying to speak to the ghost old man. The two unexplored tiles became visible, but each Mythos phase had nothing occur. No horror checks, no monster spawns. So we were able to get the Grotesque stones and place them with the next 4 turns with nothing occurring.
Anyone else see this happen?