Terror strikes the underground train system in Moscow in the form of a flood from a collapsed tunnel. The film follows a diverse group of Moscow citizens who find themselves trapped in the city’s underground rail network, their train derailed and virtually crushed after an aging tunnel collapses. Amongst this band of survivors is softly spoken surgeon Andrey (Sergei Puskepalis), whose wife is having an affair with the conceited businessman Vlad (Anatoly Beliy). Fate brings these two men together on the same doomed train, but there is little time to resolve their differences, as the tunnel begins to quickly fill with water, forcing them to work together with the others and find a way back to the surface.
On a secret military base a group of scientists have made a discovery unequaled since the invention of the A-bomb; code-named Eruptor, it's a device that supercharges Dark Matter and uses it to change the molecular structure of its target, thereby eradicating it.
Iconoclastic, take-no-prisoners cop John McClane, finds himself for the first time on foreign soil after traveling to Moscow to help his wayward son Jack - unaware that Jack is really a highly-trained CIA operative out to stop a nuclear weapons heist.
Ray Breslin is the world's foremost authority on structural security. After analyzing every high security prison and learning a vast array of survival skills so he can design escape-proof prisons, his skills are put to the test.