The Black Mesa incident did not go unnoticed and attracted the attention of the inter-dimensional empire, which, with their countless armies, managed to defeat humanity, battered by the battle with the horrors from another dimension, in just seven hours.

The story takes place either before the arrival of the Combine or after, if you prefer to choose one of the options.

Following the Black Mesa incident, humanity had been trying for days to control the advances of Xen's fauna. During this period, a large part of the world had already been affected by the wildlife. Aliens like Vortigaunts were no longer under the control of their former leader, but aliens like Gargantuas and Alien Grunts continued their attacks even after their leader's death.

Amidst these attacks, creatures like Bullsquids, Houndeyes, and even Tentacles kept attacking various locations everywhere.

After 10 days of relentless attempts to annihilate Xen—when humanity, alongside the UN, NATO, and the forces of China and Russia, thought they were finally putting an end to the threat—that was when everything changed forever

Several portals opened in the skies of various countries, and then a race known as the Combine arrived on Earth. During this period, the war had changed forever.

Now known as the Seven Hour War