Gabriel MacKenzie is a man on the edge. Troubled by the ghosts he suddenly cannot see and haunted by one he can't escape, it's his turn to seek help from old friend Martha Armstrong and her partner Will.

Who is the strange young man that leaves him mysterious messages in his apartment and that watches him sleep at night? It's a question that takes Gabriel, Martha and Will from Edinburgh's dark lanes to the majesty of the Scottish Highlands and Dubhglas Castle, once a comforting childhood retreat for the troubled medium.

Martha, too, has to confront a face from her past, a face that could change her life and that of her daughter forever. Will they find peace, and the answers they seek on the Dubhglas Estate? Or are some things best left hidden in the dark water of Dubhglas loch?

Together, they uncover the secret that shattered Gabriel's family and split a young couple apart, fifty years before. And too late, Martha learns that sometimes the dead won't harm you. But the living will...