Episode 4 AKA Return to Ravenholm. This was apparently being developed between 2006-2007 by Arkane Studios, but ultimately ceased development. Some screenshots were leaked around three years ago, and just recently some more were found in some dudes portfolio.
Quote from Marc Laidlaw on "Episode 4":
Here's a few:
Link to all of them and a video: http://www.valvetime.net/threads/ne...evealed-valvetime-spotlight-exclusive.246580/
...these new screenshots come to us via the personal portfolio of Robert Wilinski, a Senior Environment Artist at Arkane Studios between 2007 and 2008, who was likely an important component within the “Return to Ravenholm” and “The Crossing” projects. A deeper discussion of these screenshots can be found in the Spotlight Exclusive episode listed above, but feel free to take a closer look at all 11 new screenshots below! The final two screenshots we've included also highlight The Crossing, so check them out too! If you don’t know what The Crossing is or why you should care, be sure to check out our previous episode covering the topic!
Quote from Marc Laidlaw on "Episode 4":
...there was indeed a project called Return to Ravenholm. We are big fans of Arkane and wanted to come up with a project we could work on together. We threw ideas around, they built some cool stuff, but we eventually decided that it didn’t make sense to pursue it at the time. As I recall, we felt like a lot of the staples of Ravenholm–headcrabs and zombies!–were pretty much played out, and the fact that it would have to take place sometime before the end of Episode 2 (so as not to advance beyond where Valve had pushed the story) was a creative constraint that would hamper the project…and Arkane.
Here's a few:
Link to all of them and a video: http://www.valvetime.net/threads/ne...evealed-valvetime-spotlight-exclusive.246580/