Cass Lynch has achieved the post of third officer aboard her beloved Norwegian sail-training ship, Sørlandet. The change from a largely solitary life aboard her own yacht to living cheek by jowl with more than twenty strangers will take some getting used to. They're sailing from Norway to Ireland and Cass is glad to be back at sea, but something doesn't feel right. An unnerving early-morning encounter leads to suspicions that there's a stowaway aboard - yet a police search finds nobody. Then, as the ship heads for Scottish waters, one of trainees goes missing... <br/><br/>As tension mounts among the crew and Cass wonders whether more than one person is acting suspiciously, she and DI Gavin Macrae find themselves up against a ruthless killer. When faced with violence in a beautiful but extremely remote setting, Cass must follow her instincts to navigate the rising tide of mystery. <br/>