Left 4 Dead is a 2008 multiplayer survival horror game developed by Valve South and published by Valve. The game uses Valve's proprietary Source engine, and is available for Microsoft Windows, Xbox 360 and Mac OS X. Development on the game was completed on November 13, 2008, and two versions were released digitally: A downloadable digital version, released on November 17, 2008, and a digital retail disc version, with a release date determined by region. The digital retail disc version was released in North America and Australia on November 18, 2008, and in Europe on November 21, 2008.
Set during the aftermath of a zombie outbreak on the East Coast, the game puts its four protagonists—dubbed the "Survivors"—against hordes of the infected. There are four game modes: a single-player mode in which allied characters are controlled by AI, a four-player co-op campaign mode, an eight-player online versus mode and a four-player survival mode. In all modes, an artificial intelligence dubbed the "Director" controls level pacing and item placements in an attempt to create a dynamic experience and increase replay value.
Left 4 Dead was well received by the industry media upon its release, with praise given for its replay value, focus on cooperative play, and movie-like experience. Several criticisms were aimed at the limited level selection and the lack of a narrative. The game has won several publication awards, as well as distinctions from the Academy of Interactive Arts & Sciences and British Academy of Film and Television Arts. As was done with Team Fortress 2, Valve supplemented the game with free downloadable content. The first, called the "Survival Pack", was released on April 21, 2009. The second piece of DLC was charged for on Xbox Live and came in the form of a new Campaign entitled "Crash Course," released for both the PC and Xbox 360 on September 29, 2009. Left 4 Dead was released for the Mac on October 28, 2010.
The popularity of the game led to the development of a sequel, Left 4 Dead 2, which was released on November 17, 2009. A new map for both Left 4 Dead and Left 4 Dead 2, called "The Sacrifice", was released on October 5, 2010. In July 2012, all Left 4 Dead campaigns were ported over to Left 4 Dead 2, with cross-platform multiplayer support between Windows and Mac versions of the game.
An outbreak of a highly contagious pathogen nicknamed the "Green Flu" (which causes extreme aggression, mutation to the body cells, loss of higher brain functions, and essential zombification of those who catch it) begins in Pennsylvania. Memorial walls—giving names & obituaries to those who have died in the infection—suggest that the game takes place in October 2009. Two weeks after the first infection, four immune survivors—Green Beret and Vietnam veteran William "Bill" Overbeck (voiced by Jim French), college student Zoey (voiced by Jen Taylor), district account manager Louis (voiced by Earl Alexander), and outlaw biker Francis (voiced by Vince Valenzuela)—make their way out of the city of Fairfield, only to discover that the infection is creating dangerous mutations in some of its hosts.
After narrowly avoiding the new types of infected, the survivors are alerted by a passing helicopter to an evacuation point at the roof of Mercy Hospital. Fighting their way through the city's streets, subway, and sewers, they are rescued from the hospital's roof by the pilot, only to discover that he is infected. Zoey is forced to kill him, causing the helicopter to crash in an industrial district outside the city. Finding an armored delivery truck, the group uses it to reach the small town of Riverside. After encountering a hostile and delirious man in the local church, they discover that the town is overrun and head to a boathouse for rescue. Contacting a small fishing vessel, they are dropped at the city of Newburg across the river, finding much of it in flames. Resting in a greenhouse, the survivors are interrupted by a military C-130 Hercules passing overhead, leading them to believe that it will land at the city's airport. The U.S. military had bombed the airport in an attempt to contain the infection, though the runway is partially intact, allowing the survivors to fuel up and escape in the waiting C-130.
Like the helicopter before it, this plane also crashes, and the survivors find themselves at the outskirts of the Allegheny National Forest. Following a series of train tracks, the group finally reaches a functioning but abandoned military outpost. After answering a radio transmission, they make their final stand against hordes of infected before a military APC arrives to supposedly transport them to Northeast Safe Zone Echo, one of the few remaining safe areas. Instead, they are detained in a military installation, where they learn that they are not immune and are actually asymptomatic carriers who have infected most of their rescuers. Meanwhile, the base is overthrown by a mutiny, attracting hordes of infected. The survivors escape via train and travel south at the insistence of Bill, who believes they can find long-term safety on the islands of the Florida Keys.
At the portside town of Rayford in Georgia, they find a sailboat but must first raise a lift bridge powered by an aging generator to reach open waters. As the bridge raises, the generator gives out. Bill sacrifices himself to restart it so that the others may reach safety. While waiting for the horde to disperse, the three remaining members encounter the survivors from Left 4 Dead 2. They agree to help the Left 4 Dead 2 survivors re-lower the bridge so that they can cross in their car. Louis, Zoey, and Francis then board their boat and set sail for the Florida Keys.