Black Cathedral by Maynard and Sims is $0.99 at Amazon.
At an old manor house on a remote Scottish island, six managers of a large corporation arrive for a week-long stay. Within days they will all suffer horrifying deaths and their bodies will never be found. The government assigns the case to Department 18, the special unit created to investigate the supernatural and the paranormal. However this is no mere haunted house. The evil on this island goes back centuries, but its unholy plots and schemes are hardly things of the past. In fact, while the members of Department 18 race to unravel the island’s secrets, the forces of darkness are gathering…and preparing to attack.