Karl Voss, captain of German military intelligence, fulfilling the request of his father, a general who opposed Hitler and committed suicide, meets with a member of the German Resistance. As a military attaché, he ends up in Lisbon with an underground mission - to inform the British about the Germans' work on the atomic bomb. As a representative of the embassy, Foss is involved in the sale of diamonds, the proceeds from which should be used to make a bomb. Mathematics student Andrea Aspinall comes here under the guise of an employee of the Shell company. Her task is to find out how and why these diamonds are transported. The heroes met and fell in love, but aren't spy games for lone wolves?