Chapter V is largely complete, and the download has been updated! It's a very dark trip which will lead the heroes to meet Demogorgon himself, in the middle of the Temple of Insanity. When faced with a dark demigod, only skillful roleplaying can get you out alive.
Check the first post for the links. I can't guarantee on the host's reliability, but if anyone wants to mirror the files, I'd be grateful - just post the links somewhere in this thread.