Campaigns

Campaigns (or movies) are story lines consisting of several chapters (levels, maps). At the end of each chapter, players are given awards for how well they did on certain aspects. If at least one Survivor escapes after the finale, credits will roll with the Survivors' final results. Much like the awards, the credits are completely cosmetic.

Each campaign features a "finale," in which the Survivors call for help and must face a gigantic horde while waiting for rescue to arrive. This includes several waves of Common Infected and Special Infected, as well as two or more Tanks (though hardly ever a Witch). After holding off the Infected for a certain period, the remaining Survivors (if any) head to the rescue vehicle.

Left 4 Dead
Currently, Left 4 Dead has six campaigns playable in Campaign and Versus, with the seventh only available in Survival. They are, in chronological order:
 * 1) No Mercy―In Fairfield, after a narrow escape with the Infected, the Survivors focus on moving towards a Hospital for evacuation from a passing News 5 helicopter. The Survivors move from an apartment building, subway station, sewer, Mercy Hospital, right up to a Rooftop Finale.
 * 2) Crash Course―See below in Downloadable Campaigns.
 * 3) Death Toll―The Survivors have finally made it to where Riverside lies. Due to the pathway blocked on the abandoned highway, the Survivors follow the drainage system of Riverside, to a church, into the town of Riverside, and finally to a boathouse on the riverbank. There, the Survivors wait for rescue from a civilian fishing boat.
 * 4) Dead Air―With the Survivors stranded in a large greenhouse full of Infected, they witness a plane fly by overhead. Deciding the best way to escape the city is via the airport, they make their way through a metropolitan area, over rooftops, a construction site, an air station terminal, and finally, a last stand at a Runway Finale. There, the Survivors see a C-130 Hercules plane that has run out of fuel, and needs help refuelling.
 * 5) Blood Harvest―Lost in the middle of a thick forest, the Survivors follow the path to a trainyard, and through a repair warehouse. Following the railway lines, they move past a bridge, a train station, and finally to a Farmhouse Finale. With nobody in sight, the Survivors call via a radio to the military, and from there, wait for a armored personnel carrier to pick them up. But in the meantime, the Infected have discovered their location....
 * 6) The Sacrifice―Escaping Millhaven on a train, the Survivors are now busting through a dock port, a brick factory―all ending on a bridge. And "all" includes one of the Survivors' lives...

Downloadable Campaigns

 * 1) Crash Course―After escaping Fairfield in No Mercy, the helicopter crashes in an area close to The Turnpike in Death Toll. With the pilot having fallen to the Infection, one of the Survivors is forced to kill him mid-flight. Having survived the crash landing intact, the Survivors make their way across alleys to a garage where they find an armored delivery truck on top of a vehicle elevator, just out of reach.
 * 2) The Last Stand―A "what if" scenario, the Survivors have made their way to a lighthouse in hopes of rescue. But their hopes are dashed as they realize rescue will never come. With realization comes grim determination as the Survivors hold out for as long as they can....
 * 3) The Sacrifice―The aftermath of Blood Harvest and the comic are told in The Sacrifice. The Survivors arrive in a shipyard by train and must battle their way through constant hordes, an imprisoned Tank, and some rather bothersome birds in hopes of finding a working sailboat. Unfortunately, the almost flawless plan to raise the bridge and escape the largest horde anyone has ever witnessed goes awry after one of the generators malfunctions, and one of the Survivors must sacrifice themself so the others may proceed. Canonically, this Survivor is Bill, but in the campaign, anyone may do so. This is the first campaign to be released for both Left 4 Dead and its sequel.

Storyline
There is no definitive storyline involving the six campaigns (with the exception of No Mercy-Crash Course-Death Toll and Blood Harvest-The comic-The Sacrifice) in Left 4 Dead, only a collection of maps where you need to get from Point A to point B. It is unknown if Valve will ever pick up a solid story after the initial cutscene. However, the campaigns can be linked to one another with careful observations, but this does not define it as Left 4 Dead canon.

However, it is worth noting that according to the Developer Commentary, the game was originally supposed to be one large campaign, but was later split up. For example, No Mercy and Death Toll were directly linked; in the former's Rooftop Finale: the helicopter pilot reveals that he tried to do a ground pickup, but was bitten by the Infected in the process. Unfortunately, he soon dies, and the helicopter crash-lands on The Turnpike where the Death Toll campaign begins. Though most of the sound clips have been removed from the game, their audio files are still in the game files. They can be heard here. However, it is now known that the helicopter crashes in The Alleys from the Crash Course campaign, which links No Mercy and Death Toll. Death Toll also links to Dead Air because the owners of the boat kicked off the survivors.

Behind the Scenes
According to Kotaku.com, Left 4 Dead ' s campaigns used to be different. Beta Campaigns were Dead End (which resembles early Dark Carnival like settings), Drive-In Hell (which also resembles Dark Carnival) and Fair Game (again, looks like the final version on Dark Carnival), Ghost City (which includes a flooded city, like Hard Rain), Line of Fire (which shows a trailer park), Wrecked (a campaign never seen in both games which features a crusier ship) and Dead March (features a Swamp Fever-like theme).

Left 4 Dead 2
Left 4 Dead 2 currently has six campaigns playable in all gameplay modes.

The game's campaigns are listed below, in chronological order:


 * 1) Dead Center―In Savannah, Georgia, four complete strangers find themselves caught up in the chaos of a recent outbreak of the deadly Infection currently sweeping across the United States. Missing the last evacuation helicopter, they are forced to band together and head to the next known evacuation center at the mall. The Survivors shoot their way down through a burning hotel and through the Infected-swarmed city streets to a nearby shopping mall, where they find it overridden with zombies. With no other alternatives, they hope to use a famous race car being exhibited there to make their escape.
 * 2) The Passing―See below in Downloadable Campaigns.
 * 3) Dark Carnival―Upon finding the freeway out of Savannah blocked by abandoned cars, the Survivors are forced to leave their vehicle and make their way on foot to the nearby Whispering Oaks amusement park, still partially operational and crawling with Infected. As a patrolling rescue helicopter circles overhead, the Survivors must make their way down the park's midway, through the Tunnel of Love, over the tracks of a rollercoaster, and past the exhibition barns to reach the park's stadium, where the pyrotechnics display of a rock concert stage may provide them with their only means of signaling the chopper pilot for help.
 * 4) Swamp Fever―Unfortunately for the Survivors, the helicopter pilot that rescued them from Whispering Oaks succumbs to the Infection, and they are forced to kill him and crash-land the chopper in the Mississippi bayou. Finding evidence that rescue may be waiting deeper in the swamp, the Survivors must trek through an abandoned alligator farm, an airliner crash site, and a ramshackle shantytown where the local swampfolk made their last stand against the Infected. Eventually, they reach a giant plantation house, where they must hold off the relentless hordes of Infected until a kindly skipper named Virgil arrives with a rescue boat to take them to a rumored safe zone in New Orleans, Louisiana.
 * 5) Hard Rain―As the evening sun begins to set, the Survivors learn that their rescue boat doesn't have enough fuel to reach New Orleans. Virgil drops them off in the derelict town of Ducatel, Mississippi, to look for more. Their situation is further complicated by forgetting to bring signal flares to indicate that they've retrieved the fuel, as well as the sudden onset of a torrential downpour, the first sign of an incoming hurricane. The Survivors must move through suburban streets teeming with Infected and a half-demolished, Witch-infested sugar mill to reach a gas station. After obtaining the fuel, they must then make their way back through the mill and the town, both now flooded by the storm, to return to the dock, signal Virgil with the illuminated sign from a nearby Burger Tank, and escape before the full force of the storm hits.
 * 6) The Parish―Virgil, who rescued the Survivors in Hard Rain and Swamp Fever, leaves them in New Orleans as he goes in search of more Survivors. The Survivors find the city completely overrun by the Infected. They have to make their way through the streets of the French Quarter, the military's abandoned quarantine zone, and an aboveground cemetery until they finally arrive at a partially collapsed table bridge. On the other side is a military helicopter waiting to take the Survivors out of the city to a flotilla of military-commandeered cruise ships in the Gulf of Mexico, where the last remnants of humanity in the area have regrouped, safe in the knowledge that the Infected can't swim...so far....
 * 7) The Sacrifice―See below in Downloadable Campaigns.
 * 8) No Mercy―See below in Downloadable Campaigns.

Downloadable Campaigns

 * 1) The Passing ― After escaping the mall in Dead Center, the Survivors are stopped by a raised bridge. They encounter the Left 4 Dead Survivors taking shelter on the bridge, who inform the new Survivors that they will lower the bridge if the generator is refilled with gasoline. The Survivors make their way through the streets and buildings, past an interrupted wedding ceremony, through some sewers, to the generator, where they discover that one of the Survivors at the bridge has passed away. With combined effort from everyone, the generator is filled, and the Survivors are able to raise the bridge to continue their journey onwards in their stolen race car.
 * 2) The Sacrifice with No Mercy ― The aftermath of Blood Harvest and the comic are told in The Sacrifice. The Survivors arrive in a shipyard by train and must battle their way through constant hordes, an imprisoned Tank, and some rather bothersome birds in hopes of finding a working sailboat. Unfortunately, the almost flawless plan to raise the bridge and escape the largest horde anyone has ever witnessed goes awry after one of the generators malfunctions, and one of the Survivors must sacrifice themself so the others may proceed. Canonically, this Survivor is Bill, but in the campaign, anyone may do so. This is the first campaign to be released for both Left 4 Dead and its sequel. When downloaded for the latter, another campaign, the fan favorite No Mercy, becomes available as well.
 * 3) Cold Stream ― an upcoming DLC Pack which includes a non-canon campaign with ported versions of Death Toll, Dead Air, Blood Harvest and Crash Course.

Storyline
The Survivors begin their trek on the top of a hotel, watching what was supposed to be their rescue helicopter fly away, leaving them stranded in Savannah, Georgia. They make their way down to ground level via elavator, and introduce themselves on the way down. They then decide to head to a local mall said to be an evacuation station for CEDA. Along the way, they aid a middle-aged man by delivering bottles of cola in exchange for firearms and a clear path to the evacuation station. Once at the mall, they discover it overrun with Infected and the health stations destroyed. With no where else to go, they fuel up a racing stock car put up for a show and make their escape.

The Survivors now meet another group of people near a bridge, which needs to be lowered to continue; however, a generator which is on the other side of the bridge must be filled first to activate it. The Survivors then walk by a park and into a apartment complex, which leads them to a wedding gazebo, where they encounter Bride Witch. After a long walk in the once-busy streets, they are forced to move underground and through the sewers. After reaching the surface, the Survivors once again meet the second group, which tells them to collect gas canisters to fill up the generator, while they are swarmed by the Infected. When full, the bridge is lowered and the Survivors run back to the car and escape once again.

The sun has set and the car is now immobile, the Survivors are forced to travel on foot over the stopped cars. In the distance, they see search lights, so they make their way towards them in hopes there will be someone around who can help. They discover the source of the lights to be a carnival which they traverse, finding nothing but Survivor-hating Infected. Overhead, a helicopter can be heard, so they follow it until they reach a stadium, where they use lighting equipment and loud rock-and-roll music to inform the pilot of their presence. The plan works, and the Survivors are rescued by the pilot. However, this was only true until he began turning pale and attempted an attack.

In self-defense, and perhaps protecting of his comrades, Nick kills the now-infected pilot, sending the helicopter crashing near some boxcars and a shantytown located in the heart of the Mississippi swamps. The Survivors go through an abandoned swamp city, go across a river in a mechanical ferry, head through swamps and bayou swarming with Infected, and reach the swamp town. Unfortunately, the Survivors find out that the town did not last and was overrun by the Infection. Through the advice of previous Survivors' graffiti, the quartet make their way to a Plantation house, where they are able to contact a boat captain to come and pick them up. They make it out alive, and continue down the Mississippi River, on their way to New Orleans, Louisiana.

Unfortunately, their ship is running low on fuel, and is incapable of reaching New Orleans. The Survivors are dropped off on the coast of a small suburban town named Ducatel with the task to find fuel for the boat engine. Unfortunately, the gas station across the street is out of diesel and a sign tells them that the next available gas is two miles away on the other side of a Witch-infested sugar mill. Along the way, the clouds start to roll in and rain starts to fall a little. Once they've gotten the gas needed to fuel their ship, a downpour starts up, and the roads begin to flood, forcing the Survivors to find other paths among the higher ground to make it back to the docks. Left without a method of signaling the success of their mission, they use the lights of a fast food restaurant, called the Burger Tank, to alert their vessel instead. Their plan works, and they are able to make it safely back onto the boat with enough fuel to reach their destination.

After a night's rest on their floating vessel, the Survivors reach New Orleans midday and set off to a supposed military evacuation set up on Veteran's Memorial Bridge. After traveling through the city that the Infected took over, they soon become victims of their own saviors as the military begins dropping bombs in the city. After ducking and dodging bombs, they reach the bridge, where they are able to contact soldiers via a radio clutched in the hand of a dead man. They are provided clearance to cross the bridge to the evacuation vehicle on the other side of the bay. They finally find themselves flying away from their troubles, and making it out to safety as the bridge they were just on is bombed, and collapses into the bay.

Awards
Once each level in a campaign is completed, players are presented with several awards. These awards are purely cosmetic and do not affect gameplay. Only the most relevant will be shown.

Note: The following are only given in Versus Mode.
 * General Defense - Killed the most Infected.
 * Tank Slayer - Did the most damage to the Tank.
 * Least Damage Taken - Took the least amount of damage.
 * Protector - Protected the most teammates.
 * Witch Hunter - Did the most damage to the Witch.
 * Headhunter - Got the most headshots.
 * Special Killer - Killed the most Special Infected. This is only shown if there were no Tanks or Witches in the chapter.
 * Most Careful Teammate - Lowest friendly fire incidents.
 * Total Damage - Did the most damage to the Survivors.
 * Boomer Damage - Did the most damage as a Boomer.
 * Hunter Damage - Did the most damage as a Hunter.
 * Smoker Damage - Did the most damage as a Smoker.
 * Hunter Pounces - Pounced the most Survivors.
 * Tank Punches - Punched the most Survivors.
 * Most Vomit - Vomited on the most Survivors.
 * Survivor Drags - Dragged the most Survivors.

Achievements

 * See Main Article: Achievements

Left 4 Dead

Left 4 Dead 2