The terraformation of Xen has begun. The planet now supports a breathable oxygen-nitrogen atmosphere and earth-like gravity. A scientific facility called the Xeno Project has been set up on the planet for continuing research into portal technology. Tension on the planet is running high due to the secrecy surrounding the project and the military’s distrust of the scientific community. You are Gordon Freeman. Your mission is to report to the underground test lab at the Xeno Project.