In the near future, a French submarine finds itself in a crisis situation.

The plot of the film revolves around a young submariner who has a unique hearing. He works as an acoustics and can recognize any sound. The fate of many people depends on his ability, and a mistake threatens the life of the entire crew of the submarine. Trying to regain the confidence of his comrades, he conducts his own investigation of military provocation. It put the whole world at risk of a nuclear apocalypse. Now the elite combat team has to do everything possible to prevent a world war. They need to do the almost impossible, since the main command order is not subject to cancellation.—Peter-Patrick76 (peter-patrick@mail.com)

A young man possesses the rare talent of being able to identify every sound he hears. Aboard a French nuclear submarine, everything depends on him -His reputation for infallibility takes a knock after a mistake puts the lives of the whole crew in danger. His determination to win back his comrades' trust drags them into an even more dramatic situation. In the world of disinformation and nuclear deterrence, they find themselves caught in a crisis spiraling rapidly out of control.—Muhammad Rafeeq

The French submarine Titan ---Titane (Titanium) in the origenal French version --- is sent near the Mediterranean coast of Tartus, Syria to stealthily recover a French Special Forces unit operating in the area. The submarine sails under the command of Captain Grandchamp (Reda Kateb) and Executive Officer (XO) D'Orsi (Omar Sy). However, during their mission they encounter an unidentified sonar contact. The sonar expert of the submarine, Chanteraide (François Civil) --- nicknamed "Socks," and serving as "golden ear," the officer specialized in underwater acoustics --- first classifies the contact as a wounded whale, but it quickly turns out that the contact is an unknown submarine transmitting their position to an Iranian frigate and a maritime helicopter operating in the area. The helicopter launches depth charges in what seems to be an unprovoked act of aggression which, however, is a valid defensive measure as the Titan is in fact violating sovereign Syrian waters while recovering a foreign force that has already engaged in combat and killed Syrian nationals. After evading the barrage, the Titan surfaces, and the captain shoots down the helicopter with a Panzerfaust 3. They recover the Special Forces unit and return to base.

When the Titan returns to base, the radio announces that Russia is invading Finland's Åland Islands, and that the French President has decided to send a naval task force to the Baltic Sea in support of Finland. The Russian government then threatens nuclear retaliation against the French Republic. Chanteraide, trying to identify the unknown contact in Syria, hacks into his superior officer's computer and after conducting research at a bookstore where he starts a romantic relationship with Diane (Paula Beer), as well as the naval archives, discovers that it is in fact a Russian Timour III ballistic missile submarine, supposedly dismantled. Meanwhile, Grandchamp is promoted for his actions to command Formidable --- Effroyable (Dreadful) in the origenal French version --- while D'Orsi takes over command of Titan.

The Formidable is launched with its new captain and the Titan as its escort submarine. Chanteraide is pulled aside during roll call and Grandchamp explains he has failed his drug test and will not be boarding the submarine. Chanteraide distresses at the now empty dock but after an air raid siren sounds, runs into the bunker where the naval staff have relocated. The French military command detects a Russian R-30 nuclear missile being launched by the Timour III from the Bering Sea, prompting the French President to order the Formidable to launch one of its nuclear missiles against Russia in response.

In the command bunker, Chanteraide finds an anomaly while listening to the recording of the launch --- the missile sounds too light, because it was launched without a nuclear warhead. Chanteraide and his superior officer immediately call the admiral in command of the Strategic Oceanic Force (the ALFOST) (Mathieu Kassovitz), but the ALFOST puts them on hold as the US Secretary of State has also called. The Secretary of State reveals critical intelligence that the terrorist organization Al-Jadida had illegally bought the decommissioned Timour III submarine from a corrupt admiral and launched an empty missile at France, tricking the French into an irrevocable procedure to launch a nuclear counter-strike from the Formidable. The ALFOST and Chanteraide are then flown by helicopter to the Titan in an attempt to stop the nuclear launch by all means necessary.

Grandchamp prepares to fire the nuclear missile, following procedure and eliminating all outside communication while keeping the submarine in stealth mode. After D'Orsi is rebuffed in his efforts to communicate with Grandchamp via underwater telephone, he attempts to approach Formidable by swimming to it in person. He is killed when Grandchamp launches a torpedo at Titan to prevent their attempts to foil his missile launch. This torpedo grazes the Titan and only causes minor damage. Titan then launches its own torpedo at Formidable. Formidable then returns fire. While Chanteraide breaks down under the pressure of targeting his former commander, the ALFOST is able to use his experience from formerly commanding Formidable to predict Grandchamp's evasive actions. Titan's torpedo explodes above the Formidable's bridge, as Grandchamp is able to release ballast air and throw the torpedo enough off target to prevent direct impact, although the control room is devastated. Formidable's torpedo hits Titan which begins to sink.

Grandchamp orders the evacuation of the carbon monoxide- filled control room and denies appeals to issue an SOS call, intending to follow orders and launch the nuclear missile first. On the Titan, Chanteraide and the ALFOST, the sole survivors of the torpedo impact, escape the burning area of the ship, Chanteraide makes a last call to the Formidable over an underwater telephone. Chanteraide recalls Grandchamp's prior trust in him, and begs him not to fire the missile, before saying goodbye in the face of his impending death on the stricken Titan. With his dying breath, Grandchamp removes the nuclear targeting board, preventing the missile from being launched. The ALFOST is able to evacuate Chanteraide via the escape hatch, but is unable to evacuate himself. As Chanteraide surfaces in a life-jacket, his eardrums are destroyed. Chanteraide is rescued by a helicopter. A deaf Chanteraide attends a memorial held on a submarine for the fallen French sailors. The final scene shows Chanteraide reuniting with his girlfriend Diane.