Valve Time has gotten its hands on screenshots of a canceled Half-Life 2 episode (sometimes called "Episode Four") which was under development at Arkane Studios about a decade ago and then scrapped.
The screenshots and some commentary on how they came to be in Valve Time's possession are in the video above. Arkane Studios was working on the game, which was also known as Return to Ravenholm. About a dozen highly detailed screenshots were discovered in the portfololio of Robert Wilinski, who was an environment artist at Arkane from 2007 to 2008.
Screenshots of Return to Ravenholm have been uncovered before. This is just a bigger batch of roughly the same subjects: static environments. This episode was to have been set in a European town overrun by zombies and its events were to have taken place before the end of Episode Two.
In 2012, series writer Marc Laidlaw gave an interview in which he acknowledged that Arkane was working on the project and that it was canceled not because of any failure, but becuse Valve decided that it didn't make sense at the time to continue pursuing its completion, finding many of the themes redundant to ones already explored by the sci-fi shooter.
The individual screenshots and additional details on what they depict can be seen over at Valve Time.