November 1924. The liner Endeavour sets sail from Southampton, England, with 2,000 passengers and crew on board for a week-long voyage to New York. When an elderly man is found dead, the ship's officer, Timothy Birch, immediately considers declaring it a tragic accident. But James Temple, a determined Scotland Yard inspector, is certain it's more than just an accident. Birch agrees to investigate, and the trail quickly leads to the theft of a priceless painting. Only its owner—and the dead man—knows of its existence. With only days to go before their arrival in New York, Birch finds his search for the culprit has become increasingly perilous. Meanwhile, the passengers continue to roam the ship with a murderer among them.