Sovremennye moskovskie shkolniki Semka Voskresenskii i Sveta Larina, priotkryv zagadochnuiu dver, okazyvaiutsia v 1904 godu, v osazhdennom Port-Arture. Popav v samoe gornilo russko-iaponskoi voiny, oni pytaiutsia utcelet pod obstrelom tiazhelykh orudii, prinimaiut uchastie v spasenii admirala Makarova na gibnushchem bronenostce, popadaiut v ruki zhandarmov, okhotiashchikhsia za iaponskimi shpionami. Rebiata nakhodiat novykh nadezhnykh druzei i znakomiatsia s temi, o kom lish chitali v istoricheskikh romanakh. Chto eto takoe - neobychnoe prikliuchenie ili vstupitelnyi ekzamen v litcei khronoputeshestvennikov?