Over at the Steam Forums, a user by the name StickZero has apparently found something really very interesting. He’s found some assets in the Alien Swarm SDK that points towards growing evidence that Half Life 2: Episode 3 is in development. If you open the Alien Swarm SDK, place an info_node_hint and check the hint options you will see Aperture Nest, Blob Brain etc. Take this with a pinch of salt, but this may well be the proof Half Life fans have been waiting for to show that Episode 3 is indeed in development.
Check the image below, courtesy dl.dropbox.com.
Click the image to see it in full screen: