Good story with excellent narration.
One tiny nitpick/unasked for opinion: I think the very end of the story could be a bit stronger by rearranging a couple of the story's final lines. Have Wolf knock a couple of times and deliver the "Let me in" line, then have Charlie realize that it isn't Wolf at his door, and end the story with Worm-Wolf demanding "Let us in" and end with knocking.
Or maybe it's better the way it is. I'm no writer. Good episode my second guess aside.
P.S. For more wormy horror check out the classic Lights Out episode "Revolt of the Worms" from 1942.