Half-Life 2 Episode 3 is certainly, with Black Mesa mod, one of the most speculating game on the web. Valve, who developed Alien Swarm seems to have put Episode 3 clues in the game's SDK!!
StickZer0 opened a new topic on Steam Half-Life 2 Episode 2 forum: Half Life 2: Episode 3 found in the Alien Swarm SDK!
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