The Prime Minister of the European Monarchy of Rovenia hires Holmes to safeguard the young heir Nicholas on his journey from London to his homeland after his father the King has been assassinated. The story unfolds on board a liner and Holmes and Watson foil a series of assassination attempts and outwit fiendish plots to kidnap the Prince. As the liner slips through the fog sinister characters board the ship and Holmes has to use all his cunning to keep the Prince from harm and deliver him safely to Algi..
