Since the release of Penumbra: Overture, which was originally to be the first of a trilogy, the series appears to have changed course by cutting back to two episodes. Today Black Plague, the second and now "final" Penumbra installment was officially announced by the game's publisher, Paradox Interactive.
While not much is known about the story of Black Plague so far, it will presumably continue where its first-person horror-adventure predecessor left off. In Overture, a letter received from a father long since believed dead leads the main character to the frozen north and down a mysterious metal hatch, leaving human civilization behind and searching for clues in his father's footsteps.
Penumbra was originally developed to showcase a new technology and the unique physics found in Overture will continue in Penumbra: Black Plague. The game is scheduled for release in the first quarter of 2008.