Twine can be the perfect tool for creating some fun & interactive Halloween themed stories.
Take a look at some of these samples, all of which come from the itch.io section tagged for Twine (and Halloween).
A Series of Interactive Stories Where No Matter What You Do You Are Immediately Killed by a Werewolf: https://lukevburns.itch.io/you-are-immediately-killed-by-a-werewolf (I like these because they are short, focused, and...deadly!)
Detective Corgi and the Mysterious Mansion: https://broomcupboard.itch.io/detective-corgi (I like this because...Corgi!)
Hollowed Weed (A Study in Human Traditions, Entry 1): https://beauprime.itch.io/human-traditions-1
Consider how you might take a traditional Halloween story (spooky!) or even a traditional fable or fairytale...or an urban legend (which is really just a modern take on the former) and use TWINE to enhance it. Don't just use TWINE for a straight retelling of the story. Instead, consider how TWINE can be used to take the story down different paths, and also how the features in TWINE could be used to enhance that story via the inclusion of images, sound effects, videos, additional textual information, and more! In other words, take a story, but now make it your own creative work!