Penumbra II is a mod for Amnesia: The Dark Descent, created by Bgproductions.
Before Penumbra was made frictional games put out a penumbra tech demo. The events of the tech demo were different from the original games following the path of Phillip. In the first tech demo Phillip goes to find his Father in northern Greenland just like the original games, except Phillip finds himself inside the shelter instead of going through the minds. He goes through the shelter figuring out puzzles to advance when at the end he is hit on the head by somebody with a large metal object. This is were the events of Penumbra II take place after.
Extract into game’s folder and launch Penumbra_2.bat.
Report problems with download to firstname.lastname@example.org