An impossible, locked-room murder on a luxury ocean liner; the only viable suspect is Imogene Scott; to prove her innocence and find the real killer, she has to work with the man she hates most: Rufus Cotesworth.

Imogene must choose a side between the people who raised her or the man she hates most, who promises to get her the truth; when Rufus interrogates each suspect, he discovers that they're all lying about something, but only one of them is the killer.

Interpol seizes control of the investigation. Rufus and Imogene investigate the Colliers in secret.

As the manhunt for Jules intensifies, Imogene uncovers his criminal past and finds a new witness.

Imogene and Sunil pursue a lead in Malta. Rufus teams up with Leila and Teddy.

Imogene is betrayed by someone close to her as more victims fall prey to Viktor Sams.