Half-Life 2: Episode One continues the single-player story from the critically acclaimed Half-Life 2. Players slip on the battered spectacles of Dr. Gordon Freeman to engage in more alien and mutant battles from within the decaying walls of City 17. The expansion pack also focuses on freedom fighter Alyx Vance and her robotic companion, Dog, as they team up with Freeman to defeat the oppressive alien race known as the Combine. Though the add-on's length is shorter than the campaign found in Half-Life 2, offering an estimated four to six hours of play, the narrative addresses lingering questions and fleshes out the story lines of the principal characters in greater detail. In addition, the game introduces new ways to interact with the environment and includes a number of other surprises. ~ Scott Alan Marriott, All Game Guide