In the icy waters near the North Pole, the Arctic quiet is broken by the work of geologists Julia Diana Pozharskaya and Oskar Anton Rival, who are carrying out a series of hydrological tests for a Swedish expedition. They operate with explosive charges to study how the ocean behaves beneath the sea ice, a task that becomes suddenly more perilous when their snowmobile crashes and their camp is swallowed by the shifting ice. Not far away, the experimental submarine Ataman Yermak, gliding beneath the ice, faces a sudden crisis. Under the command of Captain First Rank Alexander Voronin [Viktor Dobronravov], the crew encounters strange activity and then suffers a catastrophic failure that forces them to jettison the emergency locator beacon as they slip under the waves.
In response, the Russian Navy dispatches Zapolyarye on a rescue mission. The ship is commanded by Viktor Voronin [Alexander Petrov], a man whose duty is complicated by deep family ties: his younger brother Alexander Voronin [Viktor Dobronravov] serves alongside him, sharing a fraught history that colors every decision. The operation is overseen by Counter Admiral Olshansky [Aleksei Guskov], who warns that the mission could become personal for Viktor and pressures him to avoid risks that could endanger the entire crew. Zapolyarye is equipped with a deep submergence rescue vehicle (DSRV) to aid in the rescue, and Viktor is given his father’s dive watch as a reminder of legacy and duty.
As Zapolyarye closes in on the beacon’s signal, Julia and Oskar’s signal is detected, and the submarine follows the beacon’s trail. The ship’s sonar meets an unusual intelligent response as it passes a vast pod of whales behaving oddly, and an unidentified creature moves beneath the hull. Olshansky orders an aggressive strike with torpedoes, while Viktor chooses a safer path and slips the submarine into the sea ice to hide, a tactic that narrowly keeps the crew out of harm and earns disapproval from Olshansky. The rescue operation succeeds in locating Julia and Oskar, who are brought aboard Zapolyarye, while Olshansky contemplates returning to Murmansk and leaves the decision in Viktor’s hands to press on with the search.
The krakenlike threat remains, a colossal creature that seems to haunt the submarine’s path. Zapolyarye skirts a Norwegian oil rig, only to watch the rig itself be dragged into the depths as the beast closes in. Olshansky declares this to be Viktor’s third mistake and moves to relieve him, firing torpedoes in a show of force that barely dent the monster. Viktor regains control, orders a crash dive, and slows every nonessential system to conserve what little power remains. The submarine returns to base only when it’s no longer safe to push further.
Back on board, Julia visits Viktor and explains a haunting possibility: their colleagues may have disturbed the Kraken, a primordial monster that lies in wait in the seabed. Its lair could be near the Ataman Yermak’s last known location in the Nansen Basin, and sonar now picks up a faint metallic knock in the same vicinity. Viktor decides to press onward in search of the missing vessel, with an abyss ahead and danger behind every tremor on the sonar.
To extend the search, the DSRV commanded by Koshkin [Sergey Kempo] is deployed. Among a graveyard of ships, Zapolyarye discovers the wreck of Ataman Yermak—the stern wrecked while the bow remains intact. Viktor, Alexander, and a few crew members stay aboard the Ataman Yermak to disable its secret weapon, while the more severely injured sailors are evacuated via the DSRV. Koshkin leaves a locator beacon on the hull, but toggles it off, remembering Viktor’s orders to keep the beacon active in a crisis.
Oskar offers to help Koshkin return the DSRV to the Yermak for a second attempt to reach the wreck. When the wreck cannot be located, the beacon is reactivated, and the Kraken reappears, forcing Zapolyarye to the surface. The DSRV reaches the site of the Yermak, with the Kraken still in pursuit, and Viktor and Alexander decide to activate the ship’s experimental weapon. A powerful energy beam is fired into the air, killing the monstrous threat, but the weapon self-destructs in the process, sending the crew scrambling as the bow of the Yermak plunges into the abyss. The rescue vehicle is sent spinning away as the ship detonates.
With the battle won, Zapolyarye surfaces under the command of Olshansky, and the DSRV rises with Viktor and Alexander aboard. Viktor offers the dive watch to his brother, who solemnly acknowledges that Viktor has earned it. The submarine completes its return to Kola Bay, bringing Viktor and Alexander together atop the conning tower, their bond tempered by peril, duty, and the strange, deadly ocean they faced.
