Install the override to allow House to gain control of the dam in the control room.
On the same floor, go southeast past the 2nd Tower exit (with the kitchen) and open the door to Hoover Dam Power Plant 1. It opens to a balcony with the switch that powers the East Power Plant on the western wall.
Go back topside to deal with the Legion and NCR on the eastern side of the dam.
Enter the Legate's camp to deal with Lanius. It is also possible to talk them into leaving the dam, with a Speech challenge (100 Speech) or a Barter challenge (100 Barter).
Reward: Completion of Fallout: New Vegas and the All or Nothing achievement/trophy
The Courier will spawn at Hoover Dam where immediately NCR Rangers will be fighting the Great Khans (if the Courier did not make them join them in the quest "Oh My Papa") and Caesar's Legion. The tower that must be entered will be the third one on the right. The Courier will see two NCR heavy troopers who will turn hostile if the override is planted, but they can be lied to with a Speech check of 75, allowing the override to be used without having any of the NCR soldiers turning hostile, which is easier for the escape. Once the Courier has uploaded the override, they should head left until they find the door to the main power plant, where just outside there will be an electrical switch to turn on the power for the Securitron army. The Courier should then head back in, find the key to the exit door and go back to the dam where only Legion and Securitrons remain and head east towards Legate's camp. Securitrons will be helping the Courier fight their way to the camp.
Once at the Legate's Camp, the player character must either kill the Legate and all enemies from Caesar's Legion or convince the Legate to retreat with a Speech of 100 with the choice "This battle is decided, that's why I am here." or a Barter of 100 by saying "You could take the West. *Holding* it is another matter." Instead of having to use Speech to fight him alone, the Courier now just says "Worth the gamble - now for the hard way."
Once they are done with Legate's Camp, the Courier must head back towards the gate where they must deal with General Lee Oliver and the NCR army. They can either kill Oliver and his men or convince him to surrender the dam with a Speech of 100 (House's forces are now much stronger than the NCR forces), Science of 100 (House can run the dam better than NCR), or a Barter of 100 (House agrees to protect Caravan routes and enforce fair trade practices). After dealing with Oliver, Mr. House will roll up in a Securitron Mk I, tell them Oliver and Kimball's likely fates, and end the quest and game.
Go to the Control Room in Hoover Dam and install the override chip.
Activate the eastern power plant to power the Securitron Army.
A Bit of Slap and Tickle ·A Final Plan for Esteban ·Access Powers ·All Fired Up! ·An Ear to the Ground ·Andy and Charlie ·Arachnophobia ·Arizona Scavenger ·Barton the Fink ·Bear Necessities ·Big Winner (Atomic Wrangler, The Gomorrah, The Tops, Ultra-Luxe, Vikki & Vance) ·Bounty Killer (I, II) ·Brotherhood Bond (I, II) ·Caching in at the Cove ·Cajoling a Cudgel ·Claws Mended ·Claws Out ·Dealing with Contreras ·Defacing the Humble Stone ·Democracy Inaction ·Don't Poke at the Bear! ·Eddie's Emissary ·Exhumin' Nature ·Fight Night ·Flogging a Dead Corpse ·Friend of the Followers ·Gland for Some Home Cooking ·Harder, Better, Faster, Stronger ·Hat's Entertainment ·Help for Halford ·Hidden Valley computer virus ·Highway to the Danger Zone (I, II) ·Honorary Rocketeer ·I Love Bananas ·Iron and Stealing ·Keith's Caravan Charade ·Laurifer Gladiator ·Lenk's Bad Debts ·Lily and Leo ·Long-Term Care ·Malleable Mini Boomer Minds ·Maud's Muggers ·Meeting an Equal ·Missing a Few Missiles ·Most Wanted ·Not Worth a Hill of Corn and Beans ·Old School Ghoul · A Pair of Dead Desperados (I, II) ·Papers, Please ·Pistol Packing ·Playing on the Old Joana ·Poor Meat Never Makes Good Soup ·Powder to the People ·Power to the People ·Razzle Dazzle! ·Reach for the Sky, Mister! ·Rest and Resupply ·Ringo's Caravan Rules ·Rotface's Loose Lips ·Saving (or Savaging) Sergeant Teddy ·The Screams of Brahmin ·Silus Treatment ·Short-Term Treatment ·Smooth-Talking Criminal ·The Star Showdown ·Strategic Nuclear Moose ·Straus Calls ·Strip Search ·Suits You, Sarah ·Tags of Our Fallen ·A Team of Moronic Mercenaries ·Thought for the Day ·Tourist Traipse ·Trudy's Radio Repair ·A Trusted Aide ·Useless Baubles or Fancy Trinkets? ·We Must Stop Beating Like This ·We Must Stop Meeting Like This ·Wind-Brahmin Wrangler ·You Gotta Break Out a Few Eggs ·You Make Me Feel Like a Woman
Sierra Madre Grand Opening! · Find Collars (8: "Dog", 12: Christine, 14: Dean Domino) ·Fires in the Sky ·Strike Up the Band ·Mixed Signals ·Trigger the Gala Event ·Put the Beast Down ·Last Luxuries ·Curtain Call at the Tampico ·Heist of the Centuries ·Big Winner, Sierra Madre
A Family Affair ·Arrival at Zion ·Bighorners of the Eastern Virgin ·Chaos in Zion ·Civilized Man's Burden ·Crush the White Legs ·Deliverer of Sorrows ·Departing Paradise ·Flight from Zion ·Gathering Storms ·Gone Fishin' ·Happy Trails Expedition ·Prisoners of War ·Retake the Bridge ·River Monsters ·Rite of Passage ·Roadside Attraction ·Sanctity of the Dead ·The Advance Scouts ·The Treacherous Road ·The Grand Staircase ·Tourist Trap
All My Friends Have Off Switches ·A Brain's Best Friend ·Coming Out of Her Shell ·Field Research ·He Came... And Went ·Influencing People ·Midnight Science Fiction Feature! ·Old World Blues ·On the Same Wavelength ·Picking Your Brains ·Project X-13 ·Sonic Emitter Upgrade ·Welcome to the Big Empty ·What's in a Name? ·When Visitors Attack! ·X-2: Strange Transmissions! ·X-8 Data Retrieval Test ·X-8: High School Horror! ·X-13: Attack of the Infiltrator!