Frictional Games are preparing re-release of Penumbra series. The Penumbra Collection consist of Penumbra: Overture, Penumbra: Black Plague and the expansion Penumbra: Requiem.
Penumbra series belongs to the horror adventure genre. It have many unique features like "I won't tell you about them". If you want to know more check this: http://www.penumbragame.com/
Seriously just follow the link or Plague will get you.
This re-release will be contained in one installer instead of three. Additional to this there will be only one serial number needed to run the game. It's such a big improvement over previous releases that needed three downloads and three serial numbers.
There is even more important information. During re-release weekend(Friday the 17th to Sunday the 19th) Linux version of Penumbra Collection will only cost 5$.