1913 Former police inspector Alexander Grossmeister, by chance, becomes an agent of Russian counterintelligence under the sonorous name of La Bruyère. His task is to be the owner of a reputable photographic establishment, which is actually a counterintelligence base. War is just around the corner, and new fortifications are being built near Riga, on Magnusholm. The Austro-Hungarian intelligence service, Evidenzbüro, sent its people to obtain plans for the fortified area. Intrigues are woven, achievements of technological progress are used, fatal seductresses use their charms... La Bruyère is inexperienced, dissatisfied with his superiors and comrades, finds himself in strange situations, but it is he who manages to uncover the spy network and receive the most valuable prize... “The Batteries of Magnusholm” is a direct continuation of the novel “An airplane for the winner.”