It is 1989 and the United States is in an economic freefall caused primarily by the world’s dwindling supply of
Night Probe
energy. CIA estimates put the depletion of the Middle East oilfields at just two years away. The total worldwide demand for oil is more than 50% of estimated supplies and while nuclear and other alternative energies are trying to make up the difference they are coming up short. Canada is now the exclusive supplier of electricity to 15 states in the northeast after investing billions in a massive new hydro-electric power plant in Quebec. To make matters worse, a top-secret experimental sub developed by NUMA has recently discovered a stratigraphic trap, potentially the richest kind of oil deposit, which lies just across the border in the territorial waters of Quebec.

Radicals in Quebec resembling the FLQ, secretly led by Canadian MP Henri Villon, are pushing for a referendum on independence from Canada. Newly elected Canadian Prime Minister Charles Sarveux fears that if Quebec declares independence Canada will disintegrate as the other provinces either follow Quebec into independence or possibly petition the U.S. for statehood.

Heidi Milligan, a U.S. Navy Lieutenant Commander, is working on her PhD in history by researching the naval policies of President Woodrow Wilson between assignments. She stumbles across a reference to a "North American Treaty" in a long forgotten letter and is intrigued when she finds out that all traces of the treaty appear to have been erased from the National Archives.

The North American Treaty, it is later revealed, was a landmark agreement between the United States and the United Kingdom. In 1914, the U.K. finds itself in economic hard times with war looming on the horizon. Fearing that the nation will not survive without a large infusion of capital, the Prime Minister, Herbert Asquith, with the cooperation of King George V, quietly approach the United States and offer, for the sum of one billion dollars, to sell Canada to the United States. President Wilson quickly agrees and pays a down payment of $150 million to seal the deal. Tragedy strikes when, on the same day in May 1914, the American copy of the treaty plunges to the bottom of the Hudson River when the steam locomotive Manhattan Limited attempts to cross a downed railroad bridge and the British copy plunges to the bottom of the St. Lawrence River when the liner RMS Empress of Ireland is accidentally rammed by a Norwegian collier. With both nation's copies of the treaty lost and the British cabinet outraged at having Canada sold off without their knowledge, Wilson orders all records of the treaty destroyed and records the $150 million payment as a war loan.

Now that knowledge of the treaty has once again emerged, the President of the United States orders NUMA and Dirk Pitt to attempt to recover the copies of the treaty, which have both lain submerged for more than 70 years. The treaty becomes the cornerstone in the President’s plan to save the United States from national bankruptcy by proposing an audacious plan, to merge the United States and Canada into one nation, "the United States of Canada."

The British see the loss of Canada to the United States as the start of the unacceptable and unthinkable disintegration of their Empire. If Canada is allowed to leave the Empire, so too might Australia, or even Wales and Scotland. The British Secret Intelligence Service recalls one of their best former agents, Brian Shaw, from retirement and orders him to keep an eye on the American salvage efforts and to ensure the destruction of the North American Treaty at all costs.