Death in Shetland waters

Cass Lynch has achieved the post of third officer aboard her beloved Norwegian sail-training ship, Sørlandet. They're sailing from Norway to Ireland as part of the Tall Ship's race. An unnerving early-morning encounter leads to suspicions that there's a stowaway on board - yet a police search finds nobody. Then one of the trainees goes missing - Cass and her lover DI Gavin Macrae find themselves up against a ruthless killer. Cass also needs to confront her personal dilemma - if she wants a settled life with Gavin, she'll have to leave the sea, but could she bear to do that?