What a great episode. I think as a sum of its parts this is the best episode, but Zima blue beats it with a perfect plot. This episode has a great plot, great characters, a cool art style for the humans and great effects for everything else, amazing atmosphere and score, great performances, great twists and great concept. I also love how the ending subverts your expectations by not having a twist/cliffhanger, which I think was really cool. Overall, very well-written and made episode, 9/10.