The Whisperer in Darkness by Howard Phillips Lovecraft

The story is told by Albert N. Wilmarth, an instructor of literature at Miskatonic University in Arkham. When local newspapers report strange things seen floating in rivers during a historic Vermont flood, Wilmarth becomes embroiled in a controversy about the reality and significance of the sightings, though he sides with the skeptics. Wilmarth uncovers old legends about monsters living in the uninhabited hills who abduct people who venture or settle too close to their territory.