Every year, on average 23 people disappear without a trace from cruise ships.

 No one has ever come back.

 Until now.

 Five years ago police psychologist Martin Schwartz lost his wife and son. They were holidaying on a cruise ship when they simply vanished, the case written off as a straightforward murder-suicide.

 They are not the only parent-and-child pair to have disappeared from the ship in recent years - and yet, the authorities seem unconcerned.

 But when a missing girl reappears - carrying Martin's son's beloved teddy bear - the police won't be able to avoid the truth that something sinister is lurking on board...