Original 'Left 4 Dead' developer, Turtle Rock Studios, has released an unfinished campaign that was never included in the final retail product. The campaign called 'Dam It', was made available to download as an add-on to the original game for free by the studio.

Valve's 'Left 4 Dead' was first launched in 2008. It has been 8 years since it was released by Valve. With the 'Dam It' add-on, original developer Turtle Rock Studios, is giving long-time Left 4 Dead players something new to return to the game and enjoy. Tech website Engadget and, gaming websites GameSpot, Polygon, IGN, and PC Gamer, covered this story.

You can play the last released campaign for 'Left 4 Dead' right now. It is free for gamers who own the game on PC. If you have a PC copy, you can download, install, and play Dam It for free. The campaign is unfinished and unpolished but it is playable. All you need is 'Left 4 Dead' and internet access to download the files and play. Turtle Rock Studios co-founder Chris Ashton posted a link in the company forums, to a third-party site where the campaign can be downloaded.

The campaign was made available as an add-on. Installation instructions for Dam It is on the download page. There are two ways to install it, the manual way and the automatic way. The automatic install only requires you to unzip the (.vpk) file and then double click the file to launch it. The manual install needs you to unzip the (.vpk) file and then copy it to the 'Left 4 Dead' 'add-ons' folder.

The campaign starts at an airfield then proceeds to an apple orchard then into a deep ravine, a covered bridge, and then a campground before the climactic fight and big finale at the hydroelectric power dam. Unlike other 'Left 4 Dead' campaigns, players are encouraged to split up but still stay close to support each other. 'Dam It' connects the stories of two campaigns, Dead Air and Blood Harvest. The campaign includes two standalone survival maps that were never released.