In the summer of 1812, Napoleon's army of almost 600 thousand in three columns invaded the territory of the Russian Empire. The goal of the Northern Army, led by Marshal MacDonald, was the Riga Fortress as the main support base of the Russian army in the Baltic states. However, the prudent marshal relied not only on the power of his regiments, but also on the help of some influential persons in Riga itself, interested in eliminating the Russian administration. By chance, friends - young officers Alexander Morozov, Artamon Vikhrev and Alexey Surkov - were drawn into a secret fight against enemy spies...