*WARNING* Gameplay segments contain spoilers!
A video from QuakeCon 2005 has been posted on the internet, showcasing id Software's Tim Willits playing through portions of Quake 4's single player campaign while a crowd watches on a projector. After the gameplay demonstration, Willits and Raven Software's Brian Raffel take questions from the crowd regarding all aspects of the game. To reiterate the spoiler warning, fans not wishing to have key gameplay points revealed to them are advised to skip ahead to the 19 minute mark, which marks the beginning of the Q & A session.
Download: Quake 4 Gameplay and Q & A
News source: PlanetQuake3.net