Destroy the source of the Mutants

Fallout main quest
Destroy the source of the Mutants
The vat teams prepare their next victim...
Location	Mariposa Military Base
Given by	Jacoren
Rewards	10000 XP
Quest chain
Previous	Find the Water Chip
Related quests	Destroy the Mutant leader Convince the Elders to send help to Mariposa

 

“Well, I'm quite impressed. My spies told me you were resourceful, but they seemed to have underestimated your talents. Guards, capture him/her!”— The Lieutenant

Destroy the source of the Mutants is a main quest in Fallout.

Quick walkthrough

Main Quest: Destroy the source of the Mutants
Learn the location of the base in the Cathedral.
Go to the base.
Use a radio to distract the mutants. (optional)
Kill the guard who has a holodisk and use it to unlock the door.
Disable the force fields. (optional)
Go to the third level and to the south elevator.
Kill the Lieutenant and Van Hagan, then loot the key.
Activate the bomb.
Get out before the bomb explodes.
Reward: 10000 XP or End of the game if completed Destroy the Mutant leader

Detailed walkthrough

If the Vault Dweller enters Lost Hills and speaks to the Elder of the Brotherhood located on level 4, or to Head Paladin Rhombus on level 1, they will both tell the player character that there are rumors of an army massing to the north. The Vault Dweller may also find a file on a military base to the north in the Los Angeles Vault, thus sparing them the trouble of searching. This will, however, require some skill with Science in order to break the files' encryption.

The military base is located a good number of squares to the northwest of the map, far from anywhere else in the wasteland. The desert surrounding it is patrolled by Unity kill-teams, equipped with miniguns, laser rifles, and rocket launchers. They may also have a few centaurs or floaters with them.

Once the Vault Dweller finally finds the massive installation, they need to get inside. There are four mutants outside the base, three with laser rifles, one with a rocket launcher. The Vault Dweller can use a radio to draw the launcher and two of the riflemen away from the base, and earn 1500 XP for tricking them. The mutant who doesn't leave holds a tape that contains the door code to the base's entrance. Alternatively, Katja can also pick the lock. Proceed to enter the main base.

Combat solution

Once inside, the Vault Dweller will most likely trigger the alarm if they are not wearing robes, and mutants will open fire on sight. However, if the alarm is not triggered by chance, one has the option to talk to the first mutant guard, who will bring them to the Lieutenant. There are four which will come running: two with miniguns, two with rocket launchers. Defeat them, then check out the forcefields. The yellow ones can be shut down for a minute by using Repair on their emitters (use repair without tools, see notes below), while the red ones can be run through at the cost of health (they are harmful).

There are two computer consoles behind a few yellow fields that can be hacked to take control of the base's security systems. The Vault Dweller can alter the robots' programming on the console near the elevator, and set his radio's frequency to match the emitters and shut them down remotely on one in the far south-eastern end of the level. Tampering with the robots will make them friendly, and changing the pest control to "large pests" will kill three mutants on the second level.

While the second level holds plenty of loot, the third level is where the Vault Dweller needs to go. They'll come across a big, suspiciously empty room. If their Traps skill is high enough, they will find all sorts of land mines and tripwires in here. The Dweller needs to get to the yellow field at the end of the hall, and blast the two mutants there: Krupper and Flip.

After taking another elevator down to level four, heading to the left will produce an encounter with Vat Team 9, a crack squad of mutant soldiers. The right leads to the vats, which is also where the Lieutenant and Van Hagan of the Children are located.

If the Vault Dweller enters the Lieutenant's office on their own, without being transported there by Flip or Harry, the Lieutenant will shoot on sight. He's armed with a powerful Gatling laser and has a whopping amount of 310 HP, while Van Hagan will snipe away with his laser pistol. If the Vault Dweller is dragged here by a mutant, the Lieutenant will interrogate and torture them, then lock them up on level 3.

The encounter with the Lieutenant is entirely optional. The vats control room is down the hallway past Vat Team 9's quarters, the room with all the COC techies. Use the terminal in the center of the overlook room to set the base to self-destruct. If the Vault Dweller's Science isn't high enough to decrypt the gibberish the terminal shows, they should pick the second one from the bottom, which sets the timer to the longest possible duration and removes yellow force fields. Alternatively, a keycard from one of the techies can be used to automatically decrypt the codes.

Infiltration solution

If the Vault Dweller is wearing some robes when they walk into the outer military base map, they can trick the mutants and get in without triggering the alarm. That will let them sneak down to the control room and blow it to pieces without wasting a single round of ammunition. Another approach is using a Stealth Boy and sneaking through, but keep in mind a high Sneak skill will be required as one cannot walk too close to the mutants or they will be detected. The Lieutenant, though, can see through the Vault Dweller's disguise if talked to.

Rewards

• 10000 XP for blowing up the base.
• Ending, if the Vault Dweller has also completed the Destroy the Mutant leader quest.

Notes

• If the Vault Dweller uses tools instead of the repair skill on the forcefield to turn them off, the game oddly enough will say the Vault Dweller lowered the field, but the field will still stay up.
• If the Vault Dweller managed to convince the Elders of the Brotherhood of Steel to help attack Mariposa, there will be three crack assault paladins waiting on the map. Each is wearing T-51b power armor, one has a CZ-53 personal minigun, another has a Gatling laser, and the third has a rocket launcher. They will follow the Vault Dweller around the exterior and blast the four mutants away, but they won't enter the base, which limits their usefulness. See Brotherhood invaders for more info.
• If Harry is alive in the watershed at Necropolis, the Vault Dweller can ask him for transportation to the base, which will avoid the dangerous journey to Mariposa (even with 100% Outdoorsman a fairly high number of super mutant patrols are encountered during travel). However, it will take you directly to the Lieutenant.
• The Vault Dweller can potentially become trapped between 2 yellow forcefields on level 2 of the base (where a group of super mutants are standing alongside some robobrains). If the Vault Dweller shuts down the southern forcefield via its keypad and passes through it without a radio, tool, or timed explosives, they won't be able to get back out. The only solution if this happens is to load an earlier save.
• The speech given by Jacoren at the end of this quest is referenced in Fallout 3 by Amata after the Trouble on the Homefront quest.

Bugs

For some unknown reason, if you do things in a particular order, when you set the self-destruct, the timer will go from whatever time you set it to zero, making the quest impossible to complete. ^[verified]

Quests in Fallout Main quests Destroy the Mutant leader · Destroy the source of the Mutants · Find the Water Chip Side quests Become an initiate · Bust the Skulz gang · Calm rebel faction · Convince the Elders to send help · Destroy the Super Mutants at the Watershed · Disarm Traps for the Facility · Dispose of Jain · Dispose of merchant · Find the missing caravans · Find the Water Thief · Fix the broken T-51b power armor · Fix the hydroponic farms in Adytum · Fix the Necropolis water pump · Free Ghoul prisoner · Get Gizmo's confession · Guard the caravans · Help Irwin · Join the Khans · Kill Killian · Kill Neal · Rescue Initiate from the Hub · Rescue Tandi from the Raiders · Rescue Sinthia · Solve Scrapheap's gang problem · Steal Neal's Urn · Steal necklace from the Merchants · Stop the Radscorpions · Stop Gizmo · Turn on power for the Glow Unmarked quests Blackmail Iguana Bob · Clean out the Loan Shark · Cure Jarvis of Radscorpion Poison · Exterminate the deathclaws · Free Adytum from the Regulators · Free the Slaves · Get weapons for the Blades · Help Saul · Improve Shady Sands' Agriculture · Kill Razor · Make Poison Antidote · Obtain more equipment · Recruit Ian · Recruit Katja · Recruit Tycho · Research important information · Save Killian's life · Scout the northern wastes · Solve Phil's Canine Conundrum · Take down Decker · Talk to Katrina · Unlock the Armory · Dr. Lorri's surgeries · Receive your weekly issue Cut content side quests Become a Blade · Deliver Locket for Romero · Deliver package from the Gun Runners · Find Children spy in the Followers · Get Sophia some pulse grenades for Michael · Report Iguana Bob to the Hub police · Rescue Jason Zimmerman · Stop the Gangs from attacking Adytum · To Catch a Wisp · The Search for the Glow · The Trade Line · Save Trish · The Wood Cutter's Wife

Mariposa Military Base Pre-War characters Robert Spindel · Roger Maxson · Platner · Robert Anderson · Erin Shellman · Steve Remco · Leon Von Felden Unity characters Lieutenant · Van Hagan · Flip · Abel · Sarah · Krupper · Stupid mutant · Lieutenant's guard Destroyed Mariposa characters Melchior · Grundel · Bracks Quests Destroy the source of the Mutants

Vault 13 Characters Cindy · Ed · Lisa · Lyle · Mary · Medic · Vault 13 overseer · Pat  · Sandy · Stacy · Susan · Theresa · Water thief · Vault Dweller · Water guard · Officer (Vault 13) · Upset vault dweller · Vault 13 citizen Quests Calm rebel faction · Destroy the Mutant leader · Destroy the source of the Mutants · Find the Water Chip · Find the Water Thief · Obtain more equipment · Research important information · Unlock the Armory