Valve send word that their free DLC for Portal 2 will arrive on October 4th. Man, I totally already said all that in the headline! Here’s what I didn’t say, which was what Valve said: “In “Peer Review”, you and a friend will continue the story of loyal bots P-Body and Atlas as you puzzle your way through a mysterious new co-op test track and once again match wits with GLaDOS. The DLC also features a single player and co-op Challenge Mode, and leaderboards to compare Challenge Mode scores with friends and the Portal community.”