Them incorporating the locked box stuff from Doctor Sleep was really cool. I knew we were going to get plot devices from other King works in this, but I honestly didn't expect a major reference to that one. Although it does make perfect sense.
The buildup of the first part of this episode was a drag but the sewer scene was what I have been waiting for this whole season. Took them long enough. Now it feels like It's got some momentum and going somewhere interesting. Ending of the episode was cool too.