How to Obtain: Visit 3 different locations with Veronica.
Associated quests: “The tall grass” and “That good old sun”
By dint of traveling with you, Veronica will end up trusting you and will start talking to you about the brotherhood (Image 1-2). After visiting 3 different locations with her, you will get the quest and be able to enter the Hidden Valley bunker, even if you don't have the quest "ED-E My Love" or if you lack persuasion. Once in the bunker of the brotherhood, go to the office of the elder and let Veronica explain herself to the big boss (Picture 3).
As you leave, Veronica will tell you about a way to change the elder's opinion about the future of the brotherhood (Image 4). Listen to her then head to the small abandoned cabin west of Gibson's junkyard (Picture 5). Inside, check out the terminal and download Elijah's data (Picture 6).
Veronica will then suggest that you go in search of an object that can convince the eldest of his mistake. You have the choice between the conducted energy weapon, the rangefinder (ARCHIMEDES System) and agronomic data. These items sometimes overlap with other quests in the game, for example, if you have completed the quest "That Good Old Sun", you will not be able to activate the unique weapon "Euclid's Chart" (Which you can still recover from a little boy from Freeside). Likewise, complete the quest "Tall Grass" destroying the Vault 22 data will prevent you from recovering the agronomic data. These quests are accessible long before Veronica's, so it's not impossible that you can only pick up the pulse gun. To find this weapon, first go to the barracks of Pearl, the leader of the Boomers (It is better if this faction is already your ally). Inside, hide and then search the lockers on the right to find a message and a key (Picture 7). Then go to Vault 34 and enter the armory (Picture 8), inside, you can use the key to open the locker room which contains the pulse pistol (Picture 9). The unique weapon in the game, the Pulse Pistol is downright deadly on bots and power armor, which you'll find out soon enough...
Return to Hidden Valley with the gun and take Veronica to the Elder (Picture 10). This one will remain camped on its positions in spite of the arguments of your acolyte who will then ask you if it should remain in the brotherhood or on the contrary join the disciples of the apocalypse (brotherhood: bonus of armor / disciples: bonus of attack) (Picture 11). When you leave Hidden Valley, a group of paladins will be waiting for you in front of the bunker (Picture 12), after some discussion about Veronica's behavior, the buggers will attack you. To get by without sores, use the magnificent impulse pistol that you have just recovered. When the paladins die, the quest ends.
Search Vault 22 agronomic data (“Tall Grass” quest)
Look for the rangefinder (before completing the quest "That good old sun without which it will be impossible to activate the "Euclid's Mire")