I've always felt that the main "monster" of this episode are at their best in horror stories, and that's something I think this episodes does very well. This episode is centred around a really cool idea and is full of genuinely creepy moments. All of the characters are great and the main setting adds so much to the atmosphere. Overall, trying to keep the review spoiler-free, this is how episodes featuring the main "monster" of this episode should be in my eyes.