Teenager Jamie Walsh boards The Sacramentum; he has paid Cormac, a Velorum crew member, to take his position onboard so he can investigate what really happened to his missing sister, who vanished from the same ship three months earlier.

Jamie wakes up with a hangover but is determined to get his investigation back on track; trusting fellow newbie Vivian enough to let her in on his real reason for being on the ship, they begin forming a plan.

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

After an unlikely ally reveals new information on Pippa's last days onboard, 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 faces a race against time, needing to rally his new friends onboard in order to save one of their own and to finally bring those responsible to justice.