Half-Life 2: Episode One is a 2006 first-person shooter game created and released by Valve for Windows. It continues the story from Half-Life 2 (2004). Players control Gordon Freeman, a scientist who must escape City 17 with his companion, Alyx Vance. Like earlier Half-Life games, Episode One includes shooting, puzzles, and storytelling.

After spending six years making Half-Life 2, Valve changed its approach to develop games in shorter parts. They focused on improving Alyx's character and her computer-controlled actions. Episode One uses a newer version of Valve's Source engine, with better lighting and animation features.

Most reviews of Episode One were positive. Playing with Alyx was especially praised, though some critics noted the game was short. It was later made available on Xbox 360 and PlayStation 3 as part of the 2007 collection The Orange Box. Episode Two was released in 2007.

Gameplay

Players move through a series of levels that follow one after another. They face enemies and meet allies along the way. The game includes both combat challenges and puzzles that use physics. In Episode One, simple tasks are added to the story to teach players new skills without making them feel like they are learning. A screen shows the player's health, energy, and ammunition. Players gain new weapons and ammunition to fight enemies. Unlike in Half-Life 2, where Gordon's first weapon is a crowbar, Gordon first gets the Gravity Gun. This tool lets him move objects from a distance during fights and puzzles.

Alyx Vance, Gordon's companion, has artificial intelligence (AI) designed to work with the player. The developers called Alyx's programming a "personality code" instead of an "AI code," showing how much effort was made to make her a unique and believable character. Alyx was programmed to avoid doing the same things over and over, like repeating lines or doing the same actions in combat. For example, in some parts of the game, players can use a flashlight to help Alyx see enemies, saving bullets. Alyx also finds good spots to shoot enemies, protecting the player while they move or do tasks.

Plot

In City 17, Gordon Freeman and Alyx Vance (Merle Dandridge) destroy the Citadel's reactor. When the reactor explodes, several vortigaunts (Louis Gossett Jr.) appear and take Alyx away. The G-Man (Michael Shapiro), who saved Gordon from the explosion, is confronted by the vortigaunts, and his mental link to Gordon is broken.

Gordon wakes up in the ruins of City 17. He is rescued from a pile of rubble by Dog and reunited with Alyx. Alyx contacts Dr. Eli Vance (Robert Guillaume) and Dr. Isaac Kleiner (Harry S. Robins), who have escaped the city. Kleiner tells them the Citadel's core will soon collapse and destroy the city.

Gordon and Alyx enter the core to temporarily fix it. Alyx finds that the Combine is trying to speed up the destruction to send a message to their home planet. She copies the message and a video from Judith Mossman (Michelle Forbes), who shares information about an unknown project before being attacked by the Combine.

Gordon and Alyx board a Combine train to leave the Citadel, but the train crashes. They go underground and travel through the city, fighting Combine soldiers and Xen creatures. Near a Combine-controlled train station, they meet Barney Calhoun (Michael Shapiro) and help evacuate people from the city. They guide the refugees to safety and take another train out of City 17, escaping just as the reactor explodes and sends the Combine's message. As the Citadel collapses, several pods carrying Advisors flee, and the explosion's force causes the train to derail.

Development

Valve created Half-Life 2 (2004) over six years using a new game engine called Source. Instead of making one large sequel, Valve chose to create shorter games released one after another. Robin Walker, a designer, explained the team felt confident with their tools and wanted to use their experience rather than invent new technologies. Gabe Newell, Valve’s president, said customers would prefer a new Half-Life game released quickly rather than waiting years for a single large game.

In April 2005, Valve announced the game with the working name Aftermath. The title Episode One was introduced in February 2006. In May 2006, Valve said Episode One would be the first of three shorter games released over the next two years. Newell compared this trilogy to Half-Life 3. He explained that in the original Half-Life (1998), the G-Man turned Freeman into his tool, and in Half-Life 2, Freeman was used by the G-Man. The episodes would show the G-Man losing control.

Marc Laidlaw wrote the stories and dialogue for Half-Life and Half-Life 2. For the episodes, Laidlaw worked with new employees Chet Faliszek and Erik Wolpaw. Valve focused on developing characters, especially Gordon Freeman’s companion, Alyx. Alyx stays with the player most of the time in Episode One. Walker noted it was ironic that the player spends much of Half-Life 2 alone, even though the game’s themes involve people and relationships.

Valve improved Alyx’s AI so she could react to the player. She comments on objects the player interacts with or obstacles they overcome. She also helps explain the story and guide the player, often telling them what to do next. Valve avoided making Alyx too disruptive, sometimes reducing her dialogue so players felt comfortable. They included “hero moments” where players could overcome challenges alone, with Alyx watching and praising them. The game was tested many times to ensure it was challenging but fair.

Episode One used an improved version of the Source engine, with better lighting and facial animation. Enemy AI was upgraded, allowing Combine soldiers to crouch while under fire to avoid being hit. The soundtrack was composed by Kelly Bailey. Music was used only during key moments, like important story scenes or large battles.

City 17 and the Citadel were changed from the end of Half-Life 2 to show the world’s transformation and the player’s impact on the story. The Citadel now looks unstable, showing the damage the player caused. This change introduces new dangers and highlights the Combine’s weakening power in City 17. City 17 also shows signs of the resistance’s rebellion, with destroyed buildings and new enemies inside, emphasizing the uprising’s scale.

Release

Episode One was sold in retail stores and through Valve's online Steam platform, where it was offered at a lower price. It was also sold separately by Electronic Arts. Players could download and buy it before the official release on Steam starting May 1, 2006. The package included Half-Life Deathmatch: Source and Half-Life 2: Deathmatch, which were playable immediately. Episode One was released again in a collection called The Orange Box, available for Mac, PC, Xbox 360, and PlayStation 3. By 2008, about 1.4 million copies of Episode One had been sold in stores. In November 2024, Valve removed Episode One and Episode Two from the Steam Store and combined them with Half-Life 2.

Reception

Response to Episode One was mostly positive. Reviewers said the game had more detailed and better timed gameplay than Half-Life 2. They also praised the way players could interact with Alyx, who reacted to the player's choices and events in the story. PC Gamer said, "Although this first episode may not be as important as Half-Life 2, no shooter fan would want to miss it." They also highlighted how the game balanced puzzles and action challenges.

Edge praised how skillfully the game guided players' attention and the strong role Alyx played as a companion. They concluded, "In a genre that often uses simple, invisible heroes, this game is very advanced." Episode One received scores of 87 out of 100 and 85.59% on review sites Metacritic and GameRankings. IGN called it "Best PC FPS of 2006" and said it offered "great value" through Valve's new episodic plan, though it did not provide the full experience of Half-Life 2. GameSpy ranked Episode One ninth on its 2006 "Games of the Year" list and noted that Alyx was shown as a believable and helpful companion.

Episode One takes about 4 to 6 hours to complete, which led to questions about whether its price was fair. Computer Games Magazine said it was hard to review the game because it is the first part of a three-part story, and its full value depends on the final product. Game Revolution was disappointed that the game did not include new features like environments or weapons. During the 10th Annual Interactive Achievement Awards, the Academy of Interactive Arts & Sciences nominated Half-Life 2: Episode One for "First-Person Action Game of the Year."

Sequels

Half-Life 2: Episode Two was released in 2007. Episode Three was planned to be released by Christmas 2007. However, it was canceled because Valve found that releasing games in parts did not match their plans for new games. They needed to focus on Left 4 Dead, which was almost finished. After canceling several other Half-Life projects, Valve released a prequel called Half-Life: Alyx in 2020.