Years after the original outbreak was contained, a new strain of the demonic infection emerges in a sprawling, abandoned subway system beneath Madrid — trapping a team of urban explorers, a disgraced scientist, and a pregnant fugitive who may hold the only key to a cure.

When a group of urban explorers live-streams their descent into the abandoned "Paco de Lucía" metro station, they unknowingly unleash a mutated form of the original agent — faster, smarter, and driven not just to bite, but to convert.

Here’s a gripping text for a hypothetical sequel, (a follow-up to the 2008 Spanish horror film [REC] — known as Quarantine in English markets): Tagline: The infection has evolved. The nightmare has just begun.

It’s been 15 years since the original apartment building was sealed off and firebombed. The world was told the "rage virus" was destroyed. But deep beneath the city, in forgotten maintenance tunnels connected to the old quarantine zone, something has been festering.