Audrey Rose Wadsworth and her partner-in-crime-investigation, Thomas Cresswell, are en route to New York to help solve another blood-soaked mystery. Embarking on a week-long voyage across the Atlantic on the opulent RMS Etruria, they're delighted to discover a traveling troupe of circus performers, fortune tellers, and a certain charismatic young escape artist entertaining the first-class passengers nightly.

But then, privileged young women begin to go missing without explanation, and a series of brutal slayings shocks the entire ship. The disturbing influence of the Moonlight Carnival pervades the decks as the murders grow ever more freakish, with nowhere to escape except the unforgiving sea. It's up to Audrey Rose and Thomas to piece together the gruesome investigation as even more passengers die before reaching their destination. But with clues to the next victim pointing to someone she loves, can Audrey Rose unravel the mystery before the killer's horrifying finale?