Sinner's Pass by SS Fitzgerald:
 
How far will a father go to get his son back?

Welcome to Sinner’s Pass …

A small town, barely a speck on the map, but those who are condemned there rarely return.
When a single father sends his only son to stay the summer with his parents in his childhood hometown, he is immediately worried by a cryptic letter from his son. He must now go to the godforsaken town to seek out his son. There, he will be forced to face not only his family’s history and demonic creatures lurking in the dark, but his own internal demons. Without honesty, there can be no redemption. Without redemption, there is no leaving the evil within Sinner’s Pass.