The adventure ends here, this is all puzzles and no story at all.
Penumbra: Requiem is a puzzle game, nothing wrong with that though, but it's the types of puzzles to solve. Each level pits you in a random environment with different mechanics to solve a puzzle and collect "keys" which open the exit portal of each level. The puzzles are mostly made of flipping switches, throwing boxes around and platform jumping. Most are easily solvable because you only need common sense to get through, although sometimes there are tedious moments such as meddling with the physics engine, climbing ladders and trying to spot hard to find items to finish some puzzles (pieces of metal, batteries, fuses etc..) as items no longer go into your inventory when you pick them up, you "hold" them and bring them to where you need to use them.
Speaking of inventory... it's function has become completely unnecessary now. Your battery never runs out for the flashlight, there are no interesting stories to read in the journal, and the only items you can store in the inventory are painkillers and artifact statues.
The graphics and sounds are unchanged since Black Plague.
If you are planning to get this game, don't expect any adventure or rpg elements, it's a pure puzzle game that rips off the Half Life mod Portal in some aspects.