Michael McLaren returns home from working a cold case in Cumbria to learn that he's missed his uncle's wedding in Scotland. Angry and fearful that his absence has re-opened the family rift just as it's healed, he drives to the ancestral home, hoping his appearance and explanation will be accepted. He's more than welcomed. His uncle asks him to investigate the murder of his first fiancée.
Fiona Lennox was found in a rowboat on a Scottish loch, shot to death during a late night photo shoot. Why would she rent a boat after dark? Did she take it out to photograph the moonlight on the water? She could've done, being a professional photographer, but she was also a proponent of civic and environmental causes, which she documented with her camera. Did someone linked to one of her crusades kill her, or was the motive personal?
As McLaren uncovers layers of Fiona's life and the reason for her nocturnal outing, he and his family are targets of intensifying attacks. But it's not until he races against a kidnapper's deadline and the threat of a loved one's death that he realizes who killed Fiona¾implications that are as deep and dark as the Scottish loch.