Back to School is a full featured Left 4 Dead and Left 4 Dead 2 campaign. The storyline is not interfere with none of this games and offer completly new setting of Borden city, struggling to survive in an epidemic apocalypse alongside with original 4 heroes. They are getting a chance to save themselves, since USA marines are coming in town and not falling back this time. But during the battle apogee something goes terribly wrong and local school - the most safe place in city - turns out to be a death trap.
Helicopter pilot lines from the No Mercy campaign, which were cut during the development of L4D, but remained in the game files. We have used these lines in one of the scenes of our campaign, but they had no relevant effects.