Hitler has approved a plot to abduct Roosevelt, Stalin and Churchill as they arrive for the Teheran Conference in November 1943. The plot involves ransoming off the lives of the Big Three for ceasing hostilities in Europe and recognition by the Allies of current borders and military gains by the Third Reich.
The operation succeeds and Roosevelt and Churchill are abducted. Stalin escapes the attempt with injuries. Roosevelt and Churchill are spirited away by low-flying aircraft to a remote site in Turkey, then taken by train through the Balkans to a mountain hideaway in the Austrian Alps.
Now Hitler has a bargaining chip for dealing with the U.S. and the U.K. He also knows about the proposed Operation Overlord and one of his conditions is that Overlord be scrapped.
A rescue effort must be mounted. Vice President Henry A. Wallace must coordinate with King George VI of England to coordinate rescue operations.
A combined British-U.S. commando team must try to rescue them. How do you get FDR and Churchill out if you can get rescue forces in? The team must airdrop in from a base in southern Italy.
Operation Titan is formed. The special ops team will parachute into the Austrian Alps and meet up with local resistance forces, who will provide supplies, ammo, and escape transport. The plan is to take FDR and Churchill in disguise to Venice by truck (disguised as a military supply truck). They will then be extricated by British submarine.
What the commandos haven't counted on are two obstacles that may prevent the rescue: a Resistance girl's love for an American agent. And the resourceful Nazi commander of the hostage mission, who seems to anticipate every move the Allies make.