Alpine Creek

Alpine Creek is the first chapter in the customised Cold Stream campaign which was subsequently released in beta format as a DLC offering in March 2011.

The chapter opens with a reversed cutscene, showing players the route to be followed. The survivors begin by standing in the bed of a fast-moving stream or creek flowing through a wooded area. In single player, the human player starts equipped with a single Pistol, two AI Bots will have Submachine guns and the third will also have a single Pistol. Health and a melee weapon (usually an Axe) are available under the water next to the starting point (note that the human player will not have the usual option of picking up a Pump shotgun or Submachine gun at this stage). If playing as Nick, Ellis will make a general statement to the group that he learned to use a gun before he learned to walk, and if the human player takes Nick's character, Ellis will follow this up with a jibe about Nick's suit.

Once ready, survivors head down the bed of the stream and almost immediately encounter larger-than-normal infestations of Common Infected and Mud People interspersed with Special Infected (chiefly Chargers, Spitters, Jockeys and the occasional Smoker). Since the Submachine gunners represent the core of the team's firepower, but they are AI Bots, it is a good idea for a human player to let them take down the heavier opposition. Once underway and the first enemies are encountered, Rochelle and Nick will begin to recycle on a repetitive basis the lines they used in Swamp Fever concerning mud and Mud People.

After a short distance, the creek bed opens out. Players should climb the left bank and proceed forward until they see a forestry lookout tower. A horde will spawn at this point. Climbing the tower and entering the lookout will reward players with supplies such as Gas Cans. Leaving the tower, players will spy the supporting posts of the swing bridge, seen earlier in the opening cutscene. After cleaning out the infected milling around below (e.g. with the help of a Gas Can), survivors cross the bridge to the next area. Off to the left is a small hut, which should be searched for supplies and weapons (e.g. a Hunting Rifle). Then, survivors enter the two-story forestry building, featured in the introductory cutscene. This building will usually contain minor supplies (e.g. an adrenaline shot) and an Axe. After going up the stairs, survivors will look out of the window into an area thick with Common Infected and Mud People. They will aggressively respond to the survivors' presence by swarming forward and climbing up to the window. A Charger is also likely to spawn and do likewise. This combat is relatively easy, as all a player has to do is to allow them to approach closely, and defend the window as they climb up one behind the other. If the Hunting Rifle was secured earlier, the area can be sniped from the window until it is free of immediate threat.

Once it is safe to do so, survivors drop down from the window (which is a "non-return" feature in the chapter) and tiptoe across a fallen tree trunk, spanning a deep forest pit. Up ahead is a bunker with a sliding door. One player pushes back the bunker door whilst hordes materialize from the forest outside, and from the bunker below. Since it takes a little while for the bunker door to open, infected are numerous, and one player is preoccupied with pushing the door open, this crescendo event can be quite intense. Once the bunker door is open, players must jump down into the bunker and blast their way through the bunker horde to reach the safe room at the end of the underground tunnel - all the while pursued by an unending forest horde.

Overall, the fighting in this custom chapter is more intense than is the case in a comparable standard Left 4 Dead 2 equivalent; indeed, there are few of the "quiet moments" that are fairly normal in a standard L4D2 chapter. In addition, the team's starting firepower is considerably weaker, while the numbers and aggression of the enemies encountered are both noticeably enhanced.