Alien Trilogy: Section 1[www.gamemaps.com] is a custom L4D2 map based on the 1996 game Alien Trilogy for the PSX, Sega Saturn, and PC by Fox Interactive, Acclaim Entertainment, and Probe Entertainment. The game itself was fairly good for its time, but it is indicative of many 90s FPS's. As such, it follows the old DOOM-style formula of finding a key (in this case, finding a switch or battery) to open up a random door to find another switch or battery to open up another section where you must find yet more switches and batteries. This is back when cinematics and storylines comprised very little of a game's appeal, and where the majority of the gameplay came from learning the layouts of the maps and strategizing against specific enemy placement. The maps were also often very convoluted. Because of the vast differences in gameplay style over the years, the conversion of Alien Trilogy to L4D2 is, to be honest, pretty bad. This is because many of the things that gave the original game its appeal simply don't work in L4D2.

The main reasons for this are because everything looks the exact same, there is no map or location indicators, it is consistently dark and grey, it has quite heavy fog, there are very few points of reference and distinguishable objects, and the few points of reference that do exist are connected via mazes of bland, dark corridors. Almost every hallway for the first three maps looks the exact same, and when you're confronted with junction after junction in foggy darkness with no clear path to take, it can be extremely frustrating figuring out where to go, or even where you are.

Why did I decide to make a guide for this map in particular? Well, first off, this campaign freakin' needs it because it's so dark, convoluted, labyrinthine, and has so many switches and locked doors it makes my head spin. On top of that, I'm a big Aliens fan, and I've written walkthroughs for Aliens-related games before. I also feel connected to the 90s generation of gaming; this not only includes 90s FPS's of course, but also the tradition of text-based walkthroughs. Because, sure, there's a YouTube walkthrough of this campaign that you could watch just as well as read this, but people such as myself remember and contributed to sites like Gamefaqs with the text walkthrough tradition that we learned from things like Prima Strategy Guides. This required being able to convey everything the reader needs to know through words alone. That's also why there are no in-game screenshots in this guide. And lastly, "Alien Trilogy: Section 1" was the very first L4D2 custom map that I tried out years ago with my friend Bloodmind90x (I've since played over 200). We couldn't even get through the second map so we called it quits, even though we did have fun blowing stuff up. So now, I finally decided to make a walkthrough detailing where to go and what to do, to help people like myself who were lost but wanted to know the way.

Disclaimer: This is obviously not an Expert Realism guide or anything like that. If you choose to play this on Expert Realism and this guide doesn't help you from getting killed over and over again, don't blame me. I also won't detail strategies about which weapons you should take or how to kill certain infected. This is simply a walkthrough about how to get through the maps.

Without further ado, let's begin.

To add this custom campaign to your game, follow these steps.

• Go here[www.gamemaps.com] and download the campaign.
  
• Go to your addons folder. The directory should be something like this: YourDrive:\Program Files (x86)\Steam\steamapps\common\Left 4 Dead 2\left4dead2\addons
  
• Open the campaign .zip file, and extract the .vpk to your addons folder.

Now when you open up your game, you should see Alien Trilogy in your Add-ons folder and you should be able to select it when you choose a custom campaign for either coop or single-player campaign.

After the brief cutscene, you start off behind a door. Open it and proceed forward. Break the green crate for an item, then walk up the stairs. The corridor bends left and there are some more crates with possible items, so destroy them and hopefully you'll find a magnum or something. Primaries don't spawn here. Follow the bend and go up another small staircase. At the top are some explosive barrels; it would be a good idea to trigger them, just make sure you're out of the way of the blast. You might encounter a tank at the top of the stairs, so you might want to save the explosion for if it spawns.

At the top of the stairs, go forward until you see a horizontal line of barrels in front of you and a switch on the left. Activate the switch and go into the room on the left. There will be another switch in here; hit it. Detonate the row of barrels from this room; when the door shuts, you'll be safe from the fire. Once that's done, go into the room directly opposite the room you're in. Inside will be primaries and possibly a healing item. From this room, go out the door and head to the right, the path opened up by detonating the barrels.

This will end in two paths leading to the left and right and a closed door in the wall directly in front of you. Open the door and enter the room. There are some supplies in some of the green crates. At the very back of this room, there is a battery. Press 'use' on it to pick it up. This will call a horde. Once dealt with, take the exit out the door in the back of this room. Follow it straight as you see red lights and the corridor bends to the right. Continue down some stairs until you reach a locked door, an ammo pile, and a switch to the left, which says that batteries are needed to power up these large buttons. Now that you have the battery, press 'use' on the switch to unlock the door.

When the door opens up, you'll see another four-way junction. This time, head off to the right. Go up some stairs and trigger some explosive barrels. Wait for the fire to die down, then continue along that path. Ignore a locked door on your right, then go up a short staircase. Follow the path until you reach another switch. Push it, then go through the door directly opposite the switch. This will open up to a steep staircase leading down with a gold-colored ceiling. Head down the staircase.

Once at the bottom, the path will bend to the left and lead to another door. Open it to enter a small, dark room with switches and explosive barrels. Also in the room on the right side is another battery. Pick it up to call another horde. Once that's taken care of, press three switches in the room, which are conveniently all nice in a row. Now exit this room, go back up the stairs, and through the door at the top.

At the top, exit and go left and look immediately to your left again. There are some explosive barrels and crates blocking off a path down a similar-looking staircase as before, so destroy them and wait for the fire to die out. After that, head down the staircase that was blocked by the obstructions. You'll reach a fork in the road. Take the right path. Look for two doors on both the right and left sides of the hallway. Go into the door on the right, then grab what you want in the small room and activate another switch. Then head into the room on the left side of the hallway, which has the big blue map table from Aliens and a Weyland-Yutani logo at the back. Grab ammo and supplies in this room, then put the battery into the terminal on the left side of this room. A horde will be called.

When you're done with the horde, exit out the room, turn to the right, then make a left to go back up some stairs. Turn right at the top and proceed down this corridor as it bends to the right and down some stairs. Keep following the path straight, ignoring a side passage to the right, and going down another small staircase. At the four-way junction, turn to the right and open the door. Inside is the safe-room.

From the saferoom, there are some crates immediately outside. Break them to try and get some supplies, then turn to the left. Go up one set of stairs. You'll see the path continues forward but with debris on the right and left. There will be supplies all around, so grab them and then turn to the left and bust through several walls of debris. Once you reach a door on your left with a path forward and to the right, take the door on the left. There will be an ammo pile just inside.

Go down some more stairs, then at the junction, make a left. There will be a staircase with a railing on the left. Go up it. Follow the upper path along until the you reach some orangish-red walls. When the path gives you the option to go to the right, instead stay on the left side and continue forward. Keep following the path until you reach some explosive barrels. Destroy them. When the fire dies down, go through and enter a room with a switch. Hit the switch.

Turn back around, go up the steps, and turn to the left at the first option. Go forward and at the next available time, make another left. Around here will be a battery, so make sure you pick it up. Then make another left until you're in a room that's much more wide than it is long. Its walls are also a different shade of grey. Anyway, go around the left corner to find some cots and possibly supplies and a series of blue monitors on the walls. At the end of this room is a terminal with a battery symbol. Activate it to turn on the power. Now go through the door right next to the button.

Past the door, you'll be back in the section with the orangish-red walls. Make a right and go forward. Then at the four-way junction, make a left. You'll see a sign that says "REC AREA." Go through the doorway on the left to enter a large room with a lowered section with some water in the middle. Follow either path, left or right, then through another doorway and up some stairs. Both lead to the same place, a switch. Activate it and some lights will turn on. Go back down the stairs and exit this room the same way you entered.

As you leave, turn to the right. At the junction, make a left and go up a short staircase to pick up some more ammo. Turn around and go straight forward, down the hall with orangish-red walls. At the end, you'll reach two doors, one on the left and one directly in front of you. The door on the left goes back to the room with the cots, so check that one last time for supplies if you need, otherwise go through the door straight in front of you. This is the mess hall, with cafeteria tables with the "W" symbol on them. Explore this area a bit until you find a side passage in the back with a slope going down to a small, blue, circular room with four switches. Activate them in order from right to left. The last one on the left will be inactive even when you push it; don't worry, we'll be coming back for it.

Once you've pressed all the switches, find a hole in the back of this room between two switches. Drop down. You'll be in a room with a lot of green crates. Break the crates to find the last switch. Activate it. Find the exit out of here, which is a sloped corridor. Follow it as it twists and turns until you reach a door. This opens back up to the mess hall with the "W" tables. From your position, go forward and through the doorway on your right to go back into the room with the four switches. The button on the left will now activate when you press it. This will call a horde.

When you're done with that, go to the path that is to the right from the room with the four switches. It leads up another sloped path and has a big sign that reads "PERSONNEL." At the top will be a column. Follow the path around the column to the left to find an ammo pile, then head around the column to the other side to find a door. Open it to reveal the saferoom.

From the saferoom, go forward and you'll immediately be at a four-way junction. Go forward until you reach another four-way junction. Take the left path to a large room. Near the doorway are four switches. Three you can activate, one requires a battery. Activate the ones you can for now, search for an ammo pile in the back of the room, then exit the way you came in.

As you exit, turn to the left and take the first door you see on the right, which opens up into a room with flashing blue lights. Search this room for a battery, which should call a horde. Once that's over, go back to the large room with the four switches, then activate the switch that required a battery. Now activate a fifth switch on one of the other sides of the room. Exit this room the same way you entered and turn to the right.

Go back down to the very beginning of this map, by the first four-way junction, and turn to the right. The door at the bottom of the small staircase will be open. Inside should be Tier 2 weapons. Go out this room and straight forward to the other side. Follow the series of grey corridors until it splits between left and forward. Continue forward, then follow it as it bends to the right and left again.

On the left side, you'll see a door. Open it to enter a room with some monitors and glass encasements, which you can open for supplies. Exit out of any of the doors and continue following the path to the left, which leads down. When you get to a path with orange walls, head to the right and go through a door. This will open up into a room with some crates. Break them and head to your right. This will take you down a set of stairs with some flashing red lights.

You'll reach some more green crates with a wall in front of you and a staircase to your left. Break through the wall in front of you with your right mouse button and continue forward. Do the same for the next wall you find. Walk up the lit staircase and up another one. Break another wall, then go through a door. The first junction has a path forward, a path to the left and a door on the right. The door on the right opens up to the saferoom.

From the saferoom, take the left path, then quickly make another left and follow it until you reach a room with alien eggs and a switch. Activate the switch, then turn around. Head out and to the left again. You'll come across an ammo pile. Take another left to find a section with blue walls, grey boxes, and green crates. Around here is another battery. Pick it up. This will call a horde.

Once the horde is dealt with, exit out this section again to the left. Follow the path around some explosive barrels, then around a couple big, brownish-grey columns. You should find a switch in a corner between two walls. From the switch, turn around, head to the right, and take another right to the other side of a large wall. At the end of the wall is a lift. Get on and it will take you up.

The lift takes you to a room with two switches. Hit both. This forms a bridge to take you to a switch that requires a battery. Put the battery in, then fall down to the right (the side with the explosive barrels). Follow this path straight until you reach the end, which will have a tall staircase with a railing next to a large wall. Take the staircase up. The end of the staircase will have a dropoff with some debris. Drop down. You may encounter a tank around here.

Immediately to your left should be a switch. Hit it. Nearby, across from it, is another switch. Hit it and ride the lift down. Down here are two rooms, both with switches. Hit the switches in both rooms. I haven't quite figured out how the switches work, but eventually the lift should take you up. Back on the ground floor, look to your right and you'll find a forklift. Across from it is a blue wall concealing a switch for it. Activate the switch, then climb on the forklift raisey-thingy, then take it up. Note that every time it goes down, the switch will have to be activated again for the next player, so it's best to bring everybody along at once, or wait for the bots to teleport to you.

Optional: If you want more weapons, follow these directions (otherwise, just continue forward along the upper path). At the top is yet another switch; hit it to lower a section of this path. Drop down, then take a right and enter a small room with some Tier 2 weapons and a switch. Activating the switch will activate a lift just outside the room to take you up top again.

Back on the upper walkway, continue to a staircase leading down with some explosive barrels. Destroy them if you want. Immediately on your right is a section blocked off with green crates; destroy them to find a switch and hit it. Now go past the area with the explosive barrels to find some APCs on the right. Follow the right-hand path around the APCs to find a door.

The door opens up to a grey corridor. Take the right path and continue down two sets of stairs with red flashing lights. You'll reach a familiar junction with a path on the left and a blocked off path in front of you. Break through the path in front of you twice, then head up two flights of lit staircases. Break through another path in front of you and go through a door. Take the next door you see on the right, which leads to the saferoom.

This saferoom actually has weapons, so load up before heading out. From the saferoom, head forward, then take the first staircase you see (side note: if you take a right instead, you can find a hive section with two breakable walls containing some weapons). At the end of this path, you'll find a battery. This will call a horde. Once taken care of, jump the railing on the right side (the side with the light grey tiles) to reach the start of an alien hive. Find some steps leading down into a section with some fire. There might be ammo down in the fire section but you'll take periodic damage from the fire if you go down there. Cross this section to the other side until you see some large pipes and explosive barrels. Destroy the barrels.

If you want goodies, you can take the left path first; there might be some medical supplies on a hard to reach platform--the bots can make the jump with ease, but if you choose to jump it, be sure to jump at the last possible moment both to get there and to get back. Eventually choose the path with the explosive barrels but be careful because chargers are especially dangerous here. Follow the path until you reach a T-junction with an alien hive. Take the left path.

Follow the path as it twists around. There is a breakable wall on the right side eventually, which can be broken with some shots, leading to an area with some weapons. Continue down the path until you reach a switch to the left of a Weyland-Yutani door. Hit the switch, then go through the door and take the path into the atmosphere processor.

Follow the path straight until you reach a T-junction. Make a left. Turn right when you must, follow the path, then make another right when you're again forced to. The next junction leads both straight and to the left; go straight if you need some supplies, but the path you want to go is left. Follow this all the way until you reach a door that opens up to the saferoom.

From the saferoom, head immediately to the right. Take the path as far as you can until it dead ends. Grab the battery on the left, then break through the wall and go through the door. This opens up into a room with two switches; hit them both. Go back out the way you came and keep hugging the right wall. There is another breakable wall here, which may lead to some first aid. Go back out, then keep hugging the right wall and break yet another wall.

Everything looks the same in this section but through this last wall is a static red light, which should be a point of reference for you. From the red light, go forward and head to the left. Follow the path around and eventually you'll be able to see out from little "windows" into a larger room with hive textures all over the floor. Drop down into this area.

Search the walls; next to one egg is a clearly breakable wall. Break the wall and go through the door behind it to enter an area that isn't overtaken by the hive. At first chance, make a left. At the end of this path, you'll reach a T-junction; make a right and go all the way to the end of the corridor to a switch, and hit it. Turn back around, then follow the corridor all the way to the end. Make a right to a door and go through it back into a hive.

Search the path along the left wall for supplies. There are a lot of supplies strewn all over. Eventually you'll get a custom message; activate the item to start the finale. This is a standard holdout. The best place to hang out is alongside one of the upper ledges along the wall. The place to escape to is a door that opens up along the wall. Congrats on beating the campaign!

Here are some workshop mods that you might want to consider adding to your game to give yourself a truer Aliens experience:

http://steamcommunity.com/sharedfiles/filedetails/?id=202549727
http://steamcommunity.com/sharedfiles/filedetails/?id=203295313
http://steamcommunity.com/sharedfiles/filedetails/?id=154666961
http://steamcommunity.com/sharedfiles/filedetails/?id=216687928
http://steamcommunity.com/sharedfiles/filedetails/?id=660620579
http://steamcommunity.com/sharedfiles/filedetails/?id=343622351
http://steamcommunity.com/sharedfiles/filedetails/?id=225758649
http://steamcommunity.com/sharedfiles/filedetails/?id=159836506
http://steamcommunity.com/sharedfiles/filedetails/?id=268366743
http://steamcommunity.com/sharedfiles/filedetails/?id=1065410045

http://steamcommunity.com/sharedfiles/filedetails/?id=377030811
http://steamcommunity.com/sharedfiles/filedetails/?id=122878115
http://steamcommunity.com/sharedfiles/filedetails/?id=863084009
http://steamcommunity.com/sharedfiles/filedetails/?id=473750630
http://steamcommunity.com/sharedfiles/filedetails/?id=574666145
http://steamcommunity.com/sharedfiles/filedetails/?id=577009093
http://steamcommunity.com/sharedfiles/filedetails/?id=505924883
http://steamcommunity.com/sharedfiles/filedetails/?id=326994561
http://steamcommunity.com/sharedfiles/filedetails/?id=574668868
http://steamcommunity.com/sharedfiles/filedetails/?id=574674753

http://steamcommunity.com/sharedfiles/filedetails/?id=576997524
http://steamcommunity.com/sharedfiles/filedetails/?id=909738467
http://steamcommunity.com/sharedfiles/filedetails/?id=909740233

This guide was written solely by me (Olde). However, it would not have been possible without OldSkool's walkthrough video of the campaign, which you can find here. Major credit obviously also goes to Leafo, this map's author.

You can (and should!) use this guide and share it with others. However, you should not distribute it while giving authorial credit to either yourself, someone else, or to nobody at all. You may quote from it at length but please do not post the entirety as a guide on any other forum or site without my express permission. I also reserve the right to remove or modify this guide at any time and/or make it unavailable, with or without providing a reason.

I hope you enjoyed this guide! I value your input so if you have a question or comment, please leave a post below! Thanks for reading!