Greene Township's haunted cave is traditionally thought to have been the rendezvous point for desperadoes who preyed on pioneer boats which travelled the Ohio River in the late 1700s. James Girty, brother of the infamous Simon Girty (see also Girty's Island), was the head of a band of savage robber-murderers who were responsible for a number of violent killings in Adams County in the days before whites moved into the area in large numbers. Girty, like his brother, was famous for cruelty; he was also hobbled by untreated disease, and was considered something less than human by settlers on both sides of the river. In a well-known incident, a settler named Greathouse was captured near Brush Creek in 1790, tied to a tree, and whipped to death; Girty and his band of desperadoes are thought to have been responsible. Mysterious murders at Long Lick and Brush Creek Island are also attributed to them.
The cave itself consists of a number of subterranean rooms near Black's Run, west of West Union. One of the rooms contains a clearwater spring, and the whole thing was accessible by means of a removable ladder in Girty's day. I've been unable to track down any modern mention of the cave, which was discovered during a scouting expedition for a lead mine. Maybe the mine destroyed it. Either way, it's possible that the ghost stories associated with the cave came about as a result of the very real dangers posed by the raiders who once used it as a basecamp to terrorize the southern Ohio valley.