Turtle Rock Studios the development studio formerly known as Valve South have been behind games such as Evolve and Left4Dead. The zombie slaying co-op survival game Left4Dead was one of the most successful games ever seen. Many don't realize that it was Turtle Rock behind the development of the game due to their rebrand and independence after the closure of Valve South.
Turtle Rock have surprised the millions of players of Left4Dead by releasing a new campaign for the game. The 'Dam It' campaign is releasing unfinished but is playable from start to finish and comes with two maps. Turtle Rock's Chris Ashton said "It's gray box, and some code features are missing but it's playable from beginning to end. It also includes two standalone survival maps that never shipped."
Dam It is available as an add-on, downloadable here. There are installation instructions with it but players should be aware the numerous issues abound due to it being unfinished. The page shows a nice map of the level giving you an idea of how to take on the new campaign.
'Dam it' starts off in at an airfield and then heads through areas such as an apple field, ravine, farm buildings heading to the penultimate area, The hydro-electric power station. no doubt it would have been nice to have a fully finished, polished campaign. Fans of the game however, will be pleased to receive something new after 8 years.