On average 23 people a year disappear from the world's cruise ships. They are written off as accidents or suicides. But what if they're not? 5 years ago Martin Schwarz, a police psychologist, lost his wife and son. They were holidaying on a cruise ship when they vanished. A lacklustre investigation was unable to shed any light on what happened - murder-suicide being the coroner's verdict. It is a verdict that has haunted Martin ever since, blighting his life. But then he is contacted by an elderly woman, a writer, who claims to have information regarding their fate and wants him to come on board The Sultan of the Seas immediately. Only a few months ago another mother and daughter also vanished.

She believes there may be a serial killer on board. But when the missing daughter reappears - carrying the teddy bear of Martin's missing son - it becomes apparent that the truth could be much worse.