Niamh and Ruairidh Macfarlane co-own the Hebridean company Ranish Tweed. On a business trip to Paris to promote their luxury brand, Niamh learns of Ruairidh's affair, and then looks on as he and his lover are killed by a car bomb. She returns home to Lewis, bereft. Niamh begins to look back on her life with Ruairidh, desperate to identify anyone who may have held a grudge against him. The French police, meanwhile, have ruled out terrorism, and ruled in murder - and sent Detective Sylvie Braque to shadow their prime suspect : Niamh. As one woman works back through her memories, and the other moves forward with her investigation, the two draw ever closer to a deadly enemy with its own, murderous, designs.