Approximately twenty years after being placed in stasis, Gordon Freeman is inserted into a train bound for City 17 by the G-Man (Michael Shapiro).

Helped by the undercover Resistance member Barney Calhoun (Shapiro), Gordon attempts to reach the laboratory of Dr. Isaac Kleiner (Harry S. Robins) but is subdued by Combine officers.

At the base, Gordon reunites with Alyx's father, Dr. Eli Vance (Robert Guillaume), and meets Dr. Judith Mossman (Michelle Forbes).

Gordon diverts through the zombie-infested town of Ravenholm, aided by its lone inhabitant, Father Grigori (Jim French), to a Resistance outpost whose occupants provide him with a dune buggy.

He drives along the coastline of depleted water levels to reach the Combine prison of Nova Prospekt, where Eli and Mossman are being held.

Returning to Kleiner's lab, Gordon and Alyx learn that the teleporter malfunctioned and that a week has passed, during which time the Resistance has used the attack on Nova Prospekt to launch an armed rebellion against the Combine.

Inside, a security system vaporizes his weapons but inadvertently super-charges the gravity gun; this helps Gordon climb the tower.

He is captured and taken in a transport pod to Breen's private office, near the Citadel's apex, where he and Mossman are waiting with Eli and Alyx as captives.

[6][7] Valve's president, Gabe Newell, wanted to redefine the FPS genre, saying: "Why spend four years of your life building something that isn't innovative and is basically pointless?

[6] Whereas Half-Life was set in a single location, the Black Mesa research facility, Valve wanted "a much more epic and global feel" for the sequel.

At the suggestion of the art director, Viktor Antonov, who was Bulgarian, the team settled on a city in an Eastern European location.

[6] Nova Prospekt was conceived as a small rail depot built on an old prison in the wasteland and grew from a stopping-off point to the destination itself.

The animator Ken Birdwell studied the work of the psychologist Paul Ekman, who had researched how facial muscles express emotion.

[6] The writer Marc Laidlaw created family relationships between the characters, saying that it was a "basic dramatic unit everyone understands" but rarely used in games.

[6] For several months, Newell let the team work without his input so he could provide unbiased feedback, and focused on developing Steam, Valve's upcoming digital distribution service.

The team presented the showreel to Newell, showcasing physics, environments such as the Borealis, and a dialogue-heavy scene with the scientist character Dr. Kleiner.

"[6] The graphics card manufacturer ATI had arranged a promotional event on Alcatraz Island to coincide with the planned release of Half-Life 2.

Unable to pull out of the event, Newell gave a prepared speech, demonstrated the Source engine, and left without addressing questions.

[6] On September 19, the Half-Life 2 source code was obtained by a German hacker, Axel Gembe, who had infiltrated Valve's internal network months earlier.

[7] In 2004, the team returned after Christmas to long hours, stressful working conditions, and no guarantee that Half-Life 2, which was costing $1 million a month to develop, would be finished soon.

Major changes by this point included the cutting of the Borealis, the replacement of the jet ski with a hovercraft, and introducing the physics-manipulating gravity gun earlier in the game.

[13] A demo version with the file size of a single CD was made available in December 2004 at the website of graphics card manufacturer ATI Technologies, who teamed up with Valve for the game.

[16][17] On September 20, 2004, GameSpot reported that Sierra's parent company, Vivendi Universal Games, was in a legal battle with Valve over the distribution of Half-Life 2 to cyber cafés.

On November 29, 2004, Judge Thomas S. Zilly, of U.S. Federal District Court in Seattle, Washington, ruled that Vivendi and its affiliates are not authorized to distribute (directly or indirectly) Valve games through cyber cafés for pay-to-play activities according to the parties' current publishing agreement.

The "Gold Edition" additionally includes merchandise, such as a baseball cap, a strategy guide and CD containing the soundtrack used in Half-Life 2.

[27] In 2013, Valve ported Half-Life 2 to Linux[28] and released a free update adding support for the Oculus Rift virtual reality headset.

[41][42] In September 2022, after a decade of development, fans released Half Life 2: VR Mod, allowing Half-Life 2 to be played in virtual reality.

They wrote, "Half-Life 2, everyone's default pick to win this year, is indeed a fantastic roller coaster of a ride, not as great as the original but still leagues above most other shooters.

It won the magazine's "Best Technology" (beating out Doom 3) and "Best Writing" awards, and was a runner-up in the "Best Sound Effects", "Best AI" and "Best Voice Acting" categories.

The Guardian journalist Keith Stuart wrote that it "pushed the envelope for the genre, and set a new high watermark for FPS narrative".