Plot synopsis: The year is 1943. A scientific expedition led by Professor Sagdulaev is working in the Karakum sands. In the sands, not far from them, a German plane drops paratroopers disguised in Soviet military uniforms. The saboteurs have a mission: to take explosives hidden in the ruins of an old fortress and blow up the strategic bridge over the Amu Darya. The members of the expedition engage in an unequal battle with the enemies…