Turtle Rock Studios, the studio which recently announced that they are no longer working on team based shooter game Evolve has now releaseda Left 4 Dead campaign that was scrapped from the original game. The studio was previously working on this title but Valve took over it later.
Although the game is unfinished it is playable. Here is the download link and the detailed instructions of the game.
The campaign called Dam It starts from where it ended in Dead Air. You’ll need to start from a rural airfield and escape through apple orchards, trails, camping grounds, ravines, etc. and participate in two finales – one at a logging camp and the other at a hydroelectric dam.
There are also two standalone survival maps with the campaign which were never released along with the original.