- You begin the game just outside of Vault 13. Search the bones at your feet to find a knife and some ammo. You can kill the Cave Rats in the cavern for a little bit of experience.
- Go through the long tunnel to the south to find the exit.
- Travel east toward Vault 15. Along the way you will come across Shady Sands where you can find information and equipment. The leader, Aradesh, will tell you about a Radscorpian problem they are having. Look to my side quests section for a walkthrough for this quest. Before you leave, make sure you barter for (or steal) Seth's rope.
- Continue east to Vault 15. Enter the shack and climb down the ladder to enter the Caverns outside of the Vault. You will find that the vault is abandoned and in very bad shape. Use your rope in the elevator shaft to descend.
- On the Living Quarters level, take the rope in the locker in the third room from the left and use it in the second elevator shaft to descend to the Command Center.
- Approach the rubble in the southeast corner of the Command Center level and you will conclude that you will not be able to find a Water Chip here.
- Return to the surface and leave Vault 15.
- Head to the Hub south of Shady Sands. You can find directions in Shady Sands.
- Enter the library Downtown and ask Mrs. Stapleton if she knows anything about a Water Chip. She will offer to sell you a Holodisk that can show you the location of the other Vaults where a Water Chip may be found.
- Use the Holodisk to download the information. Now, if you access your Pip-Boy, you can read the information from the disk when you click on the Status button.
- Travel east to Necropolis. You'll find the place populated by Ghouls. Some will attack when you get too close to them, but many will talk with you.
- Enter the sewer through one of the manholes.
- To the northwest you will find a small group of ghouls. Talk to their leader and you will learn that Necropolis has the Water Chip you are looking for. You can offer to help them fix their Water Pump so that they don't need the Water chip any more.
- Continue north through the sewers until you can't go any further and climb up the ladder. You should be in the Watershed area.
- Enter the building to the north where the water pump is located. You will have to fight your way through several Super Mutants.
- Enter the room next to the prison cell and descend down both ladders. You will find yourself outside of Vault 12.
- Get past the two guards and enter the Vault. Take the elevator down to the third level.
- Click on the only working computer in the southeast corner of this level. You will find the Water Chip!
- Leave the vault and return to Necropolis.
- Return to Vault 13 and report to the Overseer on the third level. He will install the new Water Chip and thank you sincerely for saving them all. He will order you to go to the library to report everything you have learned in your travels.
- Speak to the Overseer again. He will be concerned by the number of Mutants that you have encountered and suspects that someone is actually making new mutants. He will ask you to investigate this and put a stop to it.
The Brotherhood of Steel
- Travel to the Brotherhood of Steel south from Vault 13 and northwest of the Hub. Speak to Cabbot near the entrance and agree to do the quest he sends you on to become an initiate. After you have fulfilled the quest, he will unlock the door for you so that you can enter.
- Talk to General Maxson on the fourth level of the Brotherhood. He will voice concern that there is an army in the mountains to the north. Volunteer to scout out the area for him.
- One of the Elders of the Brotherhood will confide in you that he is worried about General Maxson's sanity and will ask you to investigate the mountains to the north to learn if there is any validity to Maxson's concerns.
- Leave the Brotherhood and go northwest across the desert. In the mountains near the northwest corner of the map, west of Vault 13, you will find a fortress guarded by Mutants. You can leave the Fortress without fighting any of the mutants.
- Return to the Brotherhood and report your findings to General Maxson. He will call together the elders to discuss the situation.
- Head to the council room in the northeast corner of the floor and speak to the elders. Tell them what you have discovered and convince them to make a preemptive strike against the Mutants. They will agree to your plan and will send three Paladins to help you in your assault.
The Military Base
- Return to the Military Base to the far northwest. You will be met there by three Paladins from the Brotherhood.
- Use a radio to lure the guards away and you will only have one Super Mutant left to fight. Use the holodisk found on his body to learn the passcode. When you try to open the door to the base, you will use the passcode to unlock it.
- Inside the base, you will encounter two different kinds of force fields. You can walk through the red force fields, though you will take some damage. There are three different ways to get by the green force fields:
- Use your repair skill on the emmiter right next to the force field or on the console nearby to temporarily disable the field.
- Use a radio on the northern most computer on the east side of the first level to hook it up with the reciever in the computer. You can use the radio again anywhere in the base to remotely access force field control from this computer to shut down any force fields blocking your way.
- Detonate an explosive to temporarily disable the field.
- Enter the elevator in the northwest corner and take it down to the third level. You can search the Barracks on the second level for weapons and equipment if you want, but there are a lot of Mutants here.
- Go east through the room with the mine field and then south to the holding cells. Take the elevator down to the fourth level.
- At the east end of the floor you will find the Lieutenant talking with a member of the Cathedral. Use your sneak skill to get close enough to them and you will overhear their plan to attack Vault 13. Kill them both. You will find a decoder disk on the Lieutenant's body.
- Enter the control room in the northwest corner of the level. If the forcefield is blocking your way, you can disable it by reactivating Mr. Handy in the room to the south. Use your repair and science skills on it and then instruct it to complete its task. It will be destroyed when it reaches the force field, but will short out the emitters, allowing you to pass.
- With the Lieutenant dead, the Cathedral technicians will commit suicide whenever you try to talk to one of them. Use your science skill on the computer near the center of the room to gain access to it or use the Security Card found on the body of one of the technicians. Hack into the program to unravel the encryption code and activate program 31914-1041-1251514 to initiate a 3 minute silent self destruct sequence.
- Quickly leave the Military Base before the timer expires and the base explodes.
- Enter the Library in the L.A. Boneyard where you will find the Followers of the Apocolypse.
- Talk to Nicole inside and she will share with you some of her suspisions regarding the Cathedral. If you offer to spy out the Cathedral for her, she will tell you to talk to Laura and give her the password and they will create a diversion. She will mark the location on your map.
- Leave the Boneyard and go south to the Cathedral.
- Speak to Laura in a room on the west side of the Cathedral. Give her the secret password and then follow her to a more secure location and she will tell you what she knows about the Catherdal and the Master. Ask her to show you to the secret staircase and she will go to a locked door at the back of the Catherdral, opening the locked door from the sanctuary on her way. You can also open the door yourself by bartering or pick pocketing the key from any of the people on this floor.
- Climb up the stairs in the northeast corner of the building all the way up to the top level.
- Take the black key from Morpheus either by picking his pocket or killing him for it. (You will get 1000 experience if you kill him.)
- Return to the main floor of the Cathedral and use the block key on the locked door to the back room. Open the door and climb down the stairs into the cellar.
- Use your Traps skill on the Bookcase at the end of the hallway to reveal a latch. Use the latch to open a secret passage. If you are unable to discover the latch, somebody will eventually come through the secret passage demanding your purpose in being there.
- Fight your way through all the guards and enter the Vault. If you successfully use your science skill on the computer near the Vault entrance, you can gain some experience points.
- Take the elevator up to the second floor and enter the room in the northwest corner of the level. Either convince Gideon to give you the Psychic Nullifier by asking to be anointed or kill him for it.
- Go up to the third level. On the east end, you will find a door that leads the Master's chamber. As you pass through the tunnel to the Master, you will receive damage unless you have the Psychic Nullifier in your possession.
- When you speak with the Master, don't agree to join him or give him any information or Vault 13 will be history. Just kill him. While you are fighting him, Super Mutant reinforcements will arrive regularly.
- Once the master is dead, a self-destruct sequence will be initiated and you will have to flee the Cathedral before the time expires.
- An alternate way to defeat the master is to fight your way through the barracks on the west side of the third floor and pick the locks on the doors to reach the elevator. Take the elevator down to the fourth floor and use your science skill on the computer to rig the Nuclear Warhead to blow. Again, you will have to flee the Cathedral before the time expires.