Let Sleeping Evils Lie

No one was sure whether or not the ruins beside the church at Ashley were haunted until a group of students with connections to the Ashley family, who had built the manor house the ruins had become, camped out in them in an attempt to prove that the ghosts said to haunt them didn't exist. What happened as a result of that ill conceived interference with the occult by the students, left those involved certain enough the ruins were haunted, for them to have the spirits they had encountered there exorcised.
That should have been the end of things, but as it turned out it was just the beginning. For some far greater evil than anyone involved there had ever encountered before, was set free as a result. What the students didn't know, what nobody ever knew besides the people involved at the time, was that the family fortune and the house which had been built with it, had resulted from someone making a pact with the devil back in the 1600s, when the family's fortune first began, for which their soul was forfeit at the end of the hundred years the family's fortune lasted.
What they also didn't know was that there was a get out clause in the pact which allowed the man who had made it escape the eternal damnation he had signed up for if he could find another soul, however reluctant they might be, to take his place.