Captain Carl Szokoll is one of the few to remain undiscovered after the failed assasination attempt on Hitler on July 20, 1944. He is even promoted major.
By the end of 1944 he is assigned to turn Vienna into a "fortress" and to have it destroyed before the enemy can capture the city. With like-minded officers of the Wehrmacht and in cooperartion with the resistance movement he manages to include these measures into his plans to liberate Vienna.
In order to make sure that "Operation Radetzky" works, it is indispensable to make contact with the Allies. Szokoll's closest friend, sergeant Ferdinand Kaes makes his way to the Russian headquaters. The Russians accept the plan. But in last minutes the operation is betrayed and three of Szokoll's men are hanged. Szokoll and Kaes can escape and join the underground forces.