This game is rated ESRB: Mature 17+ for Blood and Gore, Intense Violence and Language.
Crash Course is the first DLC campaign for Left 4 Dead. According to Valve it is meant to bridge the gap between No Mercy and Death Toll. Crash Course is the shortest of any Left 4 Dead campaign and contains only two chapters. Crash Course begins shortly after the events of No Mercy. The helicopter rescue pilot from the Rooftop Finale succumbs to the Infection and Zoey shoots him in mid-flight. The helicopter crashes in an industrial area outside of the city of Fairfield in Whitney County. Starting from next to the helicopter crash site, the Survivors traverse Fairfield's industrial landscape. Initially there is no firm clue about their destination until they make reference to a truck depot and discuss the town of Riverside where a military evacuation center is reported to be. This plan obviously foreshadows and contextualizes the Death Toll campaign. At the truck depot they discover an armored truck mounted on a workshop hoist which must be lowered before they can board and escape. Activating a generator for this purpose triggers a finale horde attack. In another act of foreshadowing, the generator stalls partway through the battle and one survivor must run out and restart it: the same problem occurs in The Sacrifice except the survivor who volunteers is certain to die.