An Intelligence Agent is sent to El Principe, on the border with Morocco, to investigate a possible police collaboration with a terrorist cell but finds unexpected love in the least suitable person: a drug baron's sister.

Sira Quiroga is a young Spanish dressmaker engaged to a solid suitor when a suave typewriter salesman upends her life. Spain is being upended by a civil war and the new regime's growing alliances with Nazi Germany. Sira, smart, gutsy and resourceful with a Scarlett O'Hara-like ability to whip up designer duds on a moment's notice, Sira has spunk. Sira gains and loses a small fortune, is dumped by her cad of a lover in Morocco, runs guns to get the cash to start her life anew and becomes couturier to the Nazi wives stationed in Madrid. Urged on by her friend, the real-life British spy Rosalinda Fox, Sira, too, aids the British cause.

Olmos is a corporal of the Civil Guard's Public Order and Prevention service who works in the station of his birthplace, Ezcaray, a small town in La Rioja. Robles is a lieutenant of the Rapid Reaction Group, one of the most prestigious units of the Civil Guard, an urban and modern officer. They see themselves forced to work together if they want to solve the international case which, as luck would have it, has united them in this town in La Rioja. They are polar opposites, but together they make up a great team.