Officers of the Russian Navy, lieutenant-commanders Pyotr Orlov (Marat Basharov) and Ivan Muravyov (Dmitry Ulyanov) [1] have been members of the Slavyanka submarine crew for a long time.

They used to be best friends, but during their service in Sevastopol in the 1980s, they met a beautiful girl Nelly (Chulpan Khamatova) and fell in love with her at first sight.

During an ordinary sortie Captain Gennady Yanychar (Andrey Krasko) sets a task to conduct a torpedo attack against a maneuver enemy and take evasive action keeping undetected for 24 hours.

Several crew members die in the result of the explosion, including the submarine's commander, Captain Yanychar.

The submariners decide to get out though the torpedo tube, but it turns out that only one breathing apparatus is charged and can be used; the rest are empty.