The film tells about the complex relationship between two chemical scientists. Viktor Sviridov arrived from the province, where he works as an engineer at one of the factories, at the metropolitan institute in order to defend his project related to an urgent scientific problem. However, without the support of a longtime friend Alexei Grekov, he has no chance: most members of the academic council are opposed to his project and himself. But Grekov is also forced to choose between his wife's scientific career and obligations to another.

St. Petersburg. Winter of 1917, the eve of the February Revolution. The maid finds in the room the corpse of the murdered tenant. In his pocket, a hotel account was found in the name of Karl Fischer, a well-known banker. An investigation is beginning. In the list of suspects - an agent of the secret police...

A portrait of the era of "Red Terror" during the civil war that followed the Bolshevik revolution, The Seventh Companion offers a character study in General Adamov (Andrei Popov), a law professor in the tsarist army, who is incarcerated by the Bolshevik secret police along with many other members of the bourgeoisie. Finally released into the new world of the Soviet Union, the resigned officer finds that he has lost everything from his old life except a mantel clock that he carries through the night from place to place, until he ends up back where he started.