No Mercy
The first campaign in Left 4 Dead, No Mercy spans five chapters with the first level picking up right where the game's intro cinematic leaves off; the Survivors are on the rooftop of an obliterated apartment complex, deep in the heart of the once-thriving metropolis of Fairfield and are told by a passing helicopter to get to Mercy Hospital to be evacuated. On their trek to the hospital they must endure Infected-filled apartment buildings, city streets, subway tunnels, sewers, eventually passing through Mercy Hospital where they finally reach the roof itself to be rescued by a News 5 helicopter. No Mercy is considered the most played campaign in the entire game, both campaign mode and versus.
Crash CourseA new DLC making this the second campaign in the story, it begins shortly after the events of No Mercy and spans two chapters. Valve made this change in an effort to shorten campaign play to a more reasonable time frame. The Survivors start out by the crashed remains of the helicopter that had rescued them. The helicopter pilot became Infected, and was killed by Zoey, causing the helicopter to crash into the ground. It can be assumed that during No Mercy, when the pilot says he "just had an incident," he attempted a ground pick-up and was bitten. In any case, the Survivors must make their way through the streets to a recycling center truck depot that has a modified vehicle to withstand zombie attacks. This truck is thought to be an homage to the Dawn of the Dead remake's similar vehicle. This DLC has several new features, such as a spawn timer for the infected in Versus mode and different car alarm spawn points as specified by the Director.
Death TollThe third campaign in Left 4 Dead, it spans five chapters. Set in a small town called Riverside where the Survivors believe the army might be holding out. On their trek to Riverside, they must go over a broken highway, a drain system, through a trainyard and a nearby small church. When they arrive, they must work their way through the abandoned town until they ultimately reach a boathhouse where they may finally be rescued from the ravaging horde courtesy of John and Amanda Slater.
This is the fourth campaign in Left 4 Dead, spanning five chapters. The Survivors must make their way through Newburg to a runway in hope of catching a plane from Metro International Airport to get away from the Infected. To get there, they must start their trek from a greenhouse, head past a crane, move through a construction site, traverse the airport terminal and finally reach a runway where a military C-130 Hercules airplane is waiting to evacuate them.
This is the fifth and final* campaign in Left 4 Dead. As revealed by a park sign at the starting location, this campaign takes place in Allegheny and around Allegheny National Forest in Western Pennsylvania. From here, Survivors must travel through tunnels, a large bridge, a train yard to eventually end up at a barricaded farmhouse and get rescued by the United States military. The escape vehicle is a United States military armored personnel carrier.
*The sequential order of the campaigns (excluding the first two) are only speculated at as there has not been any official comment.
