SPOILER: The house out on the purple waves
It's coming together in little pieces for me, but I think I've finally come to some matter of understanding about that house on the mountain in the middle of the purple ocean. That seems to be the White Lodge. It's the place where the Giant seems to reside, and he's the one who sends out the spirit of Laura to Earth as a counterpoint to the evil of Bob that is released. And as seen in Episode 3 of the Return, not all is good in the White Lodge now that something (possibly 'Mother') is a constant threat.
I thought BOB is the evil in the white lodge that the giant speaks of , and he locked the door and sent the lady with no eyes to trick Coop when he shows up. She convinces him to go on the roof and she flips the knife switch, which I figure changes his return path from his real body into the path into Dougie's. You see that the numbers are different when he comes back down. Maybe the lady when he comes back into the room was also sent by Bob, but I figure the one banging on the door is trying to set things straight for Coop and send him back to the right place, but BOB has locked the white lodge residents out of the room.