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A year on from the Black Mesa incident, and Gordon is working for the sinister G-Man. A second facility, Asseva Quota was established soon after Black Mesa, its aim was to research efficient ways of repelling Xen lifeforms. One scientist was examining a live Headcrab specimen, his aim was to find a way of safely removing a headcrab once implanted on a human host. The scientist was specifically studying a substance which the Headcrab injects into its victim which enables it to control the victims motions. The substance was code-named Violet. When lab rats were injected with Violet, the rats became violant and appeared to be under the control of the headcrab from which Violet was extracted. The Violet was found to evaporate and become gaseous upon contact with Nitrogen, and becomes inert 3 hours after becoming a gas form if it hadn't infected a host. The young scientist was extracting Violet from the Headcrab specimen when a minor earthquake hit the facility. While the facility was not damaged, the earthquake knocked the scientist to the floor and he dropped the canister of Violet. The canister smashed and the Violet evaporated. The Violet was sucked into the facility's ventilation system and spread. The personnel within the facility were infected and became zombie like, under the influence of the Headcrab.

Black Operatives were sent into the facility to attempt to destroy it with a Nuclear Device, however they were unsuccesful and the device did not detonate. Gordon Freeman's objective is to find and re-arm the Nuclear Bomb.

Matters have been complicated. The British and American governments have become increasingly hostile after the Black Mesa incident, the British suspecting the American government of a cover-up, and the American government denying all knowledge. The location of Asseva Quota was leaked to the British government from an unknown source, and a British task force is en-route to Asseva Quota to investigate. Freeman must stop at nothing to complete his objective, and the British soldiers are not likely to be friendly.

Features:
-Puzzling, yet action packed single player episode.
-Complete new set of enemies.
-New weapons including the FN-P90 and SA80.
-Weapons now use clips, not an ammo reserve. You best not reload half-way through a clip.
-Spirit of Half-Life technology implemented.