 After a teleport malfunctions, letting aliens from a planet called Xen into the Black Mesa research facility. Dr. Gordon Freeman who designed the teleport escapes and is coerced into working for an unscrupulous government agent known only as the G Man. Placed into stasis by the G Man, Dr. Freeeman awakes on a train heading for a massive European city known only as City 17. An alien empire called the Combine watches over an army of human minions that occupy earth and enslave it s populace, devouring its resources. And sitting within the massive fortress called Citadel that controls the oppression is none other than Gordon Freeman s old administrator, Dr. Wallace Breen. Uniting with his old acquaintances from the Black Mesa research facility, Dr. Freeman finds himself the one free man of Earth with the fate of humanity resting on his shoulders.