It's 13 months after the incidents at Black Mesa. The Black Mesa Research Facility has been shut down. The nation never got to know anything about the experiments there. The less you know, the less you worry. The government founded a new organisation to handle "alien related topics". They hired the best scientists, technicians and military forces worldwide, its name is Poke646. Some days ago the Poke646 scientists spotted alarming signals from the Xen homeworld. It looks as if the aliens plan to invade Nation City by opening a massive amount of portals. But the Poke646 Tech Labs are already prepared: some months ago the technicians developed a huge generator which is able to close hundreds of portals at once with a bundled energy beam. Four generators are about to be installed at the edges of Nation City. With all four activated they will form a giant beam and hopefully destroy the alien portal technology forever. You play the role of Damien Reeves, the technical assistant of Dr. Fuller, and you don't know all these details. All you're currently worrying about is where the hell you lost your car keys when suddenly something hits your head and you slowly fade into unconciousness. When you wake up hours later, you quickly realize that some very strange things are going on...