Cold Waters — P.M. Hubbard

Gifford knows that he must get away. London, his office job, his suburban home and his older wife have become unendurable. Then comes the answer in Callender, whom he meets in a pub and who offers him the job of handyman on a remote island. But once there doubts began to creep in. What has become of his predecessor, Mackie? Why has all the furniture been moved out of Mackie's cottage and into the one he now occupies? What secret lies inside the power house, which he has been forbidden to enter?

There is some dreadful mystery behind the isolated community on the island, and he realises that his own safety depends on remaining ignorant of the truth: that Mackie disappeared because he knew too much ...