When the lifeless body of eighteen-year-old Caitlin is discovered on a desolate beach by the Black Loch, questions of murder and secrecy shroud the tight-knit community. It soon emerges that the young woman was in an illicit relationship with Fionnlagh Macleod, a married teacher at the Nicholson Institute where she was a student. Her lover becomes the prime suspect in the murder investigation. He is also Fin's son.

Despite leaving the island a decade earlier to escape the haunting memories of his past, Fin is compelled to return to Lewis in a desperate attempt, despite the evidence, to clear his troubled son's name. He will discover that the crime is connected to his own teenage years, in a tragic salmon fishing accident that had led to two deaths, and in the growth of a multi-billion pound industry on the island.

The Black Loch takes us on a journey through family ties, hidden relationships and unforgiving landscapes, where suspense, violent revenge and revelation converge in the shadow of the Black Loch.