Why no Episode 3 ???

[WindexGlow]

Originally, penumbra was planned as 3 episodes. But their original distributor kind of screwed them out of it, and as a result they had to tone it down to 2 games (which is why black plague seems fragmenty at parts, and wraps things up quickly)

So if that hadn't happened, chances are Black Plague would have ended shortly after discovering about your fathers fate, while the third episode would have centered around trying to get to the surface and escape (or something)