Jamie pays to replace a crew member aboard The Sacramentum. He gets a crash course in ship life while keeping a low profile to investigate the disappearance of his sister from the ship 3 months earlier. A crew member is brutally attacked.

Jamie confides in Vivian as to the real reason he is on board. Grim news about a fellow crew member and the finding of a clue lead them to ask Olly for a favour - that leads to a confrontation with "The Baby" in the engine room.

It is a big day on the ship - the captain's ball, attended by the VIP guests. Jamie shares an intimate moment with Olly, while Vivian cosies up to Lily, one of the guests, risking big repercussions if she's caught.

Jamie gains an unexpected ally on board the ship, who promises him that they will investigate from the inside and get him the answers he's desperate for.

While Vivian and Lily's relationship reaches new heights, Jamie finds himself in a terrifying situation and must use all his courage and strength to escape.

Jamie finds himself in a lethal dead end with seemingly no way out. But after a surprise intervention brings some momentary respite, he learns that others are in peril.