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The Nuclear Option is the final Railroad main quest and an achievement/trophy in Fallout 4.

Quick walkthrough

Railroad Main Quest: The Nuclear Option (Railroad)
Talk to Desdemona.
Talk to Z1-14.
Kill everyone in the relay control room.
Talk to Desdemona.
Use the terminal to override the Institute lockdown.
(Optional) Issue evacuation order.
Reach the reactor.
Plant the fusion pulse charges inside the reactor.
Talk to Desdemona.
Speak to Tinker Tom.
Take Shaun with you.
Leave Shaun behind.
Step into the relay.
Use the detonator.
Talk to Desdemona.
Reward: 1500+ XP
Leads to: High Ground
To the Mattresses

Detailed walkthrough

After finishing Rockets' Red Glare, Desdemona will give this quest to the Sole Survivor. They need to fast travel to the Institute and enter the central elevator. Once arriving at the relay room, speak to Z1-14. He will tell the player character to kill everyone in the relay room (two synths and three Institute scientists). After everyone in the room is dead, Desdemona, Tinker Tom and several other Railroad members will teleport in through the relay. After talking to Desdemona, the player character will need to enter the old robotics room, a previously inaccessible door to the left of the central elevator.

After passing through this area, which includes dozens of synths, a few laser turrets and a sentry bot, the player character will arrive at the Institute Bioscience wing. After fighting their way though this wing (scientists, synths and the synthetic gorillas will be hostile), enter the main area of the Institute to join in the fight with the rebel synths from Underground Undercover to clear the area.

Tinker Tom will then come on the loudspeaker and ask to use Father's terminal to unlock the doors to the reactor. Enter Father's room and simply use the terminal to unlock the doors. One can now kill Father or leave him on his death bed with no consequences. Talking to Father beforehand and passing two speech checks can give the player character a code to shut down most of the hostile synths remaining in the main area of the Institute. Also issue the evacuation order on this terminal to allow Z1-14 and the other rebel synths to rescue non-hostile synths.

The player character will then fight through the last remaining hostile synths in the Advanced wing on their way to the reactor terminal. After disengaging the reactor lockdown on the terminal, enter the reactor and plant the fusion charge where the beryllium agitator was placed in the quest Powering Up. Tinker Tom will then teleport the player character and Desdemona back to the relay room, where Tom has found synth Shaun. Then choose between taking the child or leaving him behind.

Everyone is teleported out of the Institute to the roof of the Mass Fusion building, a safe distance away from the fusion charge's blast radius. Simply press the detonator button on the rooftop and watch the large explosion wipe out the entire Institute. Desdemona remarks that there will be retaliation from the Institute forces that managed to escape, however the Institute will never recover from the destruction of their HQ and research.

After some time, Drummer Boy in the Railroad HQ will inform the Sole Survivor that the stolen Vertibird is ready for use, and hands over three Vertibird signal grenades. More grenades can be purchased from Tinker Tom.

Quest stages

Quest stages
StageStatusDescriptionLog Entry
100 Talk to DesdemonaAfter defeating the Brotherhood of Steel, I need to check in with Desdemona to find out how we're going to deal with the Institute.
320 Talk to Z1-14It's time to finally put the Railroad's plan into action. I need to find Z1-14 in the Institute and let him know we're ready.
325 Kill everyone in the Relay Control Room
350 Talk to Desdemona
400 Reach the ReactorZ1-14 has brought Railroad members into the Institute. I need to reach the reactor and place a Fusion Pulse Charge on it so we can destroy the entire facility remotely.
430 Use Terminal to Override Institute LockdownThe only way to reach the Institute's reactor is through a terminal in the Director's quarters.
450 (Optional) Issue Evacuation Order
460 Reach the ReactorThe path to the Institute reactor is now unlocked; I need to pass through the Advanced Systems lab to reach it.
500 Plant Fusion pulse charge Inside ReactorWe've arrived at the Institute reactor. Once the Fusion Pulse Charge has been planted, we can finally destroy the Institute once and for all.
600 Talk to DesdemonaThe charge is in place; we need to get out of the Institute and reach a safe distance before it can be detonated.
700 Speak to Tinker Tom
710 Speak to Father
740 Step Into the Relay
800 Use the DetonatorWe've successfully made it out of the Institute. All that's left to do now is push the button that will destroy them completely.
900 Talk to DesdemonaIt's over. The Institute has been destroyed, and the Railroad stands victorious.
1000Quest finishedQuest complete
9000Quest failedQuest failed


  • Going through with and completing this version of "The Nuclear Option" quest does not flag the player character as an enemy of the Institute at any point, unlike getting banished or boarding the Vertibird in Spoils of War. As such, it will not make X6-88 hostile to the player character upon completion and allow him to remain as a companion afterwards. If X6 is the active companion when the mass breakout is initiated, he can even be seen relaying into the relay room alongside Desdemona and Tinker Tom, helping the player character, the Railroad and the rebel synths fight the Institute's forces. He will like telling Tinker Tom to activate the relay out of the Institute and refusing to bring the synth version of Shaun with them, regardless of which of the three dialogue options is chosen. However, aside from a single comment about destroying Father's legacy and the only hope for the Commonwealth, his dialogue will mostly assume the Institute is still around and the player character is still due to become its director. Furthermore, bringing him within close enough proximity to the Old North Church or the Railroad HQ escape tunnel entrance, or fast traveling into Railroad HQ, will still turn the Railroad hostile.
  • With the completion of Blind Betrayal prior to becoming a permanent enemy of the Brotherhood of Steel (such as when relaying to the Mass Fusion building during the Mass Fusion quest in order to maintain one's cover), Danse will not become hostile either or die alongside the Brotherhood (although he will no longer be recruitable and must be sent to a settlement beforehand in order to be at least used like a settler). Thus, completing the main quest with the Railroad is the only way to keep all 13 companions (not counting Ada, the player-made automatrons, Old Longfellow and Porter Gage) alive up to and beyond the end of the main quest.


  • PCPC Playstation 4Playstation 4 Xbox OneXbox One Teleporting into the Institute wearing a power armor helmet with the targeting HUD mod, with this quest active, makes the player character partially hostile to the Institute, denying them access to the elevator, and not spawning any Institute NPCs except Father. [verified]
    • Reloading a save from before entering the Institute, and taking off the targeting HUD mod is recommended.
    • It is possible to finish the quest without loading a previous save, by just backtracking all the way UP (without the elevator) via the way in which the quest wants you to go DOWN later on (through "BioScience" and "Old Robot") But you will need a jetpack equipped to get through a hatch in the roof one time.
    • PCPC The quest may also be completed with use of the console command tcl.
  • PCPC Playstation 4Playstation 4 Xbox OneXbox One The player character was earlier given the option to deposit weapons for the synth rebels, however upon commencing the attack, it is evident that the cache has been disregarded, and is seemingly impossible to gain access to again. [verified]
  • PCPC After the Institute detonation, the player character might experience the screen fading to black and eventually will be stuck loading the next cutscene. Use the console to relocate the Sole Survivor coc RedRocketExt (in this case, Red Rocket) and continue the game. Then type coc massfusionext02 to update the Mass Fusion building cell.[verified]
  • PCPC Xbox OneXbox One If a companion is dismissed while in the Institute, they never return home. Afterward, player.moveto finds them standing there in SRB.[verified]
  • PCPC When Tinker Tom teleports the Sole Survivor back from the reactor after they have planted the fusion charge, they may be teleported not to the relay room, but to the Mass Fusion executive suite. The detonator will be placed, but it can't be interacted with (and, as it happens, Institute quest Mass Fusion may commence). The only way to fix this is to use the console to get back to The Institute (e.g., coc institutebioscience), head back to the relay room, and talk to Tom and Shaun. (It is possible this is caused by not having done a quest to acquire the beryllium agitator.) [verified]
  • PCPC When Z1-14 is teleporting the Railroad into the Institute, if one enters the teleporter, it is possible for the player character to be immediately teleported to the Mass Fusion Executive Suite, where the detonator has yet to be placed. The only way to fix this is to use the console to get back to The Institute (e.g., coc institutebioscience), head back to the relay room, and talk to Desdemona. [verified]
  • PCPC After clearing the main area and Tinker Tom finishes announcing the lockdown needs to be raised, the central elevator may disappear while leaving the door open. If the call buttons are pressed, it will deny access. Jumping down the elevator reveals the doors are shut at the bottom. A work around is to use the “tcl” command to move through the closed elevator door. [verified]

See also