Here's another post about Provincetown.
Back in October 1938, Provincetown was haunted by a phantom that locals dubbed the Black Flash. Unlike your average ethereal wispy ghost, the Black Flash was nearly eight feet tall, unnaturally strong, and wore all black clothing, including a flapping bat-like cape. To top it off, he had glowing eyes and possibly breathed fire.
Some salient points about the Black Flash's behavior:
1. He could easily leap over 10 foot fences when being chased.
2. He liked to laugh malevolently. Once, after a villager shot him with a shotgun, he laughed AND leaped over a high fence.
3. He liked to jump out of dark alleys and scare people with his giant black cape. Sounds harmless, no?
4. He physically attacked when confronted. Two adult men both claim to have been overpowered by the Black Flash. So, maybe he wasn't harmless.
5. He terrorized P-town for seven years, until December of 1945.
The Black Flash was ultimately defeated by a group of small children. Al, Joey, Eleanor and Louie Janard were playing outside their family's house on Standish Street one foggy December day when they saw the Flash lurking on a hill nearby. Terrified, they ran inside. The Black Flash followed them, rattling the doors. Finally, Louie filled a bucket with hot water and dumped it on the phantom from an upstairs window. With a gasp, the Black Flash ran off. He was never seen again.
This story is recounted in a lot of New England folklore books, but the best account I've read is in Joseph Citro's Passing Strange. Citro in turn got his information from Robert Cahill, the now deceased Salem folklorist.
My general reaction to this story is "What the heck?" You read about a lot of ghosts and witches in New England, but not too many costumed marauders. Maybe the Black Flash was just a prankster, but he kept it up for seven years! (And apparently was immune to gunshot wounds...)
The Black Flash also seems very much like a product of his era. Costumed superheroes and villains first started to appear in the media during the Depression, and were most popular during WWII. His name and appearance remind me of Batman and the Flash, but the Black Flash's actions were a little more villainous.
*****
Author's note, 8/31/2017: I wrote this post more than eight years ago and it is still quite popular. I've learned more about the Flash since then! You can read an updated post here.

