In 1912, Holmes and Watson board the Titanic en route to America, where Holmes is to carry out a top secret government mission. Disguised as a Naval Commodore, Holmes is given the added task of looking after Christine Norton - a young and attractive secret agent - as she transports highly important submarine plans to the US navy. Soon after departure, tragedy strikes and the plans are stolen and concealed somewhere on board the huge luxury liner. The list of suspects is narrowed down to a most curious collection of passengers including a beautiful widow with an undisguised interest in Dr Watson. Most notable of them all is Colonel James Moriarty, brother of the legendary late Professor Moriarty. As the investigation continues and the plot thickens the Titanic moves swiftly across the Atlantic towards New York. But out in the distance there is a place where the sky is dark and the water is bitterly cold. A gigantic iceberg waits, ready to take on and master mankind's latest challenge to the power of nature.