Welcome aboard The Sacramentum. New recruit Jamie Walsh gets a crash course on ship life while trying to keep a low profile as he investigates what happened to his missing sister.

After shocking news concerning a chief suspect, Jamie and new friend Vivian work together to discover the identity of an officer onboard who was connected to his sister.

Jamie becomes embroiled with an illicit operation on board in exchange for new information on his sister. Meanwhile, Vivian is charmed by a guest as another crew member vanishes.

After an unlikely ally reveals new information on Pippa's last days on board, Jamie and Vivian make a shocking discovery that leads to a dangerous confrontation.

Jamie becomes a fugitive onboard, forcing his friends to hatch a daring plan, one that leads to Jamie discovering the truth about what is really happening onboard.

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.