Horizontal Collaborator takes place in Europe, from the turn of the twentieth century through World War 1. We are introduced to the eccentric lifestyle of the Hungarian nobility, which still has its roots in the feudal system, and is sharply contrasted to the childhood of Gabrielle Violette Clary, an illegitimate peasant born in the countryside of Lorraine in France.
Violette becomes a streetwise Parisienne, reveling in the unconventional café life of the period. She scratches out a living as a barmaid in Montmartre, amid surroundings that attract artists and bohemians as well as a wide variety of other characters, some intelligent, worldly people, and some who are merely bizarre. Along the way she has a youthful adventure with a handsome Hussar officer of the Austro-Hungarian Empire.
Through her dubious connections, she is presented with an opportunity to work for the French Chief of the Fifth Bureau as a double agent during the war. Despite the misgivings of the Entente, the Chief dispatches her to Spain with instructions to do what she can to infiltrate the German intelligence network, which is known to be headquartered there. After a brief training course in “spy school,” Violette boldly embarks on her ambitious undertaking armed only with her street brashness and extreme naiveté.