A Russian Navy mini-submarine with a seven-man crew is on a secret mission in the icy waters of the North Pacific on 4 August 2005. Hundreds of meters below the surface, the submarine accidentally becomes entangled in an old, discarded fishing net. The men are trapped deep underwater, and their oxygen is running out fast. Using oxygen-generating canisters, the crew devises a plan to make the oxygen last for 80 hours. The officers must breathe slowly, move little and barely speak. The men wait for hours dressed in thermal suits in 4°C temperatures, hoping for a miracle. The only rescue teams that can save them are thousands of kilometres away and are not given the go-ahead by the Russian government until after the men have already been trapped for a day. A desperate race against time by land, air and sea begins as submarine rescue teams struggle to get the equipment they need to the submarine before the officers perish.