On the eve of the Second World War, David Spaulding, a radio voice actor, is recruited by Colonel Ed Pace to run a secret network in Lisbon.

The plot advances to 1943. Both the Allies and the Axis find themselves facing key shortages that impede their ability to win the war. The Allies lack gyroscopes capable of operating at high altitudes; thus they are losing an unacceptably high number of bombers. If they do not procure gyroscopes soon, the D-Day invasion of Normandy will need to be postponed. The Germans find themselves without high quality diamonds, which are necessary for the rocket development program at Peenemünde.