A TERRIFYING MYSTERY OF THE SEA... In December 1900, three lighthouse keepers vanished without trace from the remote Scottish island of Eilean Mor. An emergency relief crew was sent to man the lighthouse. At the end of their month-long duty, they resigned from their posts and never spoke of what they had experienced on the island. The mystery of Eilean Mor has never been solved. Until now. In the present, a group of environmental researchers arrives on the island to observe the wildlife. While exploring the lighthouse, now automated and deserted, one of the team discovers a manuscript written by one of the relief keepers, a man named Alec Dalemore. As a sudden storm moves in, cutting off their escape, the researchers come to realise that Dalemore wrote the manuscript as a warning to all the lighthouse keepers who would come after him. A warning of something on Eilean Mor and in the surrounding ocean - something ancient and powerful, and strange beyond imagining...