A couple loses their children near some caves in Tijuana. The children return to their parents the next day, unharmed. However, something has happened to them.

October 2, 1968. Much to his disappointment, Ulises Martinez finds himself stranded in Martín's bus station, five hours away from Mexico City. With telephone communications and transport cut off due to abnormal heavy downpour, eight commuters are trapped within four walls, experiencing a silent, sinister undercurrent of unbridled paranoia. Now, despair gives way to violence. Does the Mexican government have something to do with the pitiless, life-altering phenomenon? Or is it all the work of unfathomable, malevolent forces?

After his best friend dies in a racing accident, biking star Joe agrees to go back on the wheels for an exhibition in Chile. On a test run with his girlfriend Stephanie, they stumble upon a badly injured man dying from a mysterious virus. That's the start of a very bad day for them as they become the target of relentless killers ready to do anything to keep their secret to go out of the mountains.