A woman seeks revenge whilst a Nazi agent seeks information, both united by a common foe: The Spanish Republic.

Shortly before the military uprising of 18th July 1936, Barcelona is a city in turmoil and both in the soldiers’ barracks and companies’ offices, conspiracy against the workers’ republic is afoot. Manfred Vogel, a German secret service agent, arrives in the city charged with building up a spy network in which an army lieutenant, José Bravo, is an important piece. When the rebellion breaks out in Barcelona, however, Bravo is one of the first to fall and Vogel loses his best agent. Fate puts him in contact with Eulalia Romá, Bravo’s young widow, full of desire for revenge and hatred of ‘This Republic of Reds and Masons’, and the pair form a surprising alliance.

Eulalia shows an unusual aptitude for clandestine work and the German agent takes it upon himself to train her, exploiting her talents and leading her to take advantage of old friendships, especially that of a young smuggler; an expert in the border passes between Spain and Andorra.

As the plot, which spans the years of the Civil War, goes on, Eulalia Romá becomes an agent infiltrated into the republican rearguard. Naïve but also implacable, she will sacrifice everything in the service of the rebellious army and that of the Germany which Vogel represents.