| || For the pre-war company, see Mass Fusion (company).|
For the location in Fallout 4, see Mass Fusion building.
|Institute main quest: Mass Fusion|
|Speak with Allie Filmore.|
|Inform the Brotherhood.|
|Relay to Mass Fusion building.|
|Leads to: Spoils of War|
|Read the terminal to locate the Beryllium agitator.|
|Retrieve the Executive keycard.|
|Proceed to the Reactor level.|
|(Optional) Restore power to the elevator.|
|Enter the reactor room.|
|Take the Beryllium Agitator.|
|Eliminate the security robots.|
|(Optional) Assist Institute forces in the lobby.|
|Exit Mass Fusion.|
|Speak with Allie Filmore in the Institute.|
|Reward: 600 XP|
|Leads to: Pinned|
Completing this quest will lead to the Brotherhood of Steel becoming your enemy. Alternatively, you could go warn the Brotherhood (thus failing this quest and starting Spoils of War instead) which will lead to The Institute becoming your enemy. Proceeding from this point will inevitably lead to one of the two factions becoming hostile.
The Institute is ready to initiate Phase Three of its long-term plans. Phase Three involves starting a new mass reactor that should resolve the Institute's ongoing power needs. To start the reactor, the Facilities division first needs to obtain a beryllium agitator, a device used to "jump-start" the reactor. Father tells the Sole Survivor to speak with Allie Filmore for the details of that operation.
Dr. Filmore explains that the Mass Fusion building in downtown Boston is known to have an agitator on-site, but retrieving it has become problematic because the Brotherhood of Steel is at the location. Allie assumes that the Brotherhood is also looking for the agitator, and she wants to make sure the Institute gets to it first. She also insists on coming, promising not to get in the way but not totally trusting the Sole Survivor with the delicate technology. If one prefers not to have her along, they can tell her flat-out that she isn't coming because she'd just be a liability. She will be insulted but will not accompany the player character.
When ready to continue, take the central lift up to the Relay room. Upon entering the relay, one should get a warning that relaying to the Mass Fusion building will make them a permanent enemy of The Brotherhood of Steel (and fail any BoS quests in progress). Continue and the player character will be teleported to the roof of the Mass Fusion building.
Upon arriving at the Mass Fusion building, there will be Brotherhood faction members present throughout the building. As with other factions, one must fight down through the building, obtaining an Executive keycard and re-routing power to the elevator when it stops. Both the keycard and the laboratory password are located in a desk on the second floor of the first room one enters. The password is used to access the executive lab terminal (also in that first room) which will tell the Sole Survivor exactly where the beryllium agitator is located within the building. For a little more backstory, grab Oslow's office recording on the table beside the terminal. Afterwards, proceed to the executive elevator in the center of the room and proceed down into the building.
While riding the elevator down, the player character will be assaulted by Brotherhood members coming out onto each floor. After several floors, they will cut power to the elevator and the player character will get the optional objective to restore power. Power can be restored either by using the development manager's terminal on the first level, or alternatively by flipping the circuit breaker located on the second level. The quest marker only points to the circuit breaker, but either method can be used successfully.
On the level with the glass floor, the Mass Fusion labs key is sitting on the desk with the active terminal. The key opens the locked door in the corner, allowing the player character to proceed downward without restoring power to the elevator. On the opposite side of the room with the glass floor, there is a ramp leading up to the next level. Directly across from where the player character comes up, there is an issue of Tesla Science laying on a console. On the other side of the second level, one will find the fuse panel where power can be restored. If the player character is wearing power armor with a jet pack, this is also a good time to get the Freefall Legs, which are located in a safe several levels up from the glass floor.
Note: If one stands in the center of the glass floor with your back to the elevator, and look down through the glass, they'll see a couch on a balcony above the large silver statue. On the head of that statue is the Strength bobblehead.
If the player character takes the restored elevator down, they'll end up at the ground floor lobby, where there is another elevator that will take them down to the reactor level. If the player character uses the key and drops down instead, they'll end up on the next floor under the glass floor. From there they'll need to fight their way down to the lobby, making sure to grab the Strength bobblehead if they haven't already. If the player character hasn't entered the building prior to this mission, there may be both Gunners and Brotherhood soldiers found on the levels, although usually the Brotherhood is pretty thorough about killing off the Gunners.
When the player character reaches the reactor level itself, they'll need to enter the chamber and remove the beryllium agitator from the reactor. The room is heavy with rads, so much so that drinking the water is instantly fatal. A hazmat suit or power armor can offer protection from the radiation. There are two hazmat suits in the area: on a locker shelf in the locker room and on top of a safe in the small office under the stairs next to the entrance to the reactor chamber. There is also a damaged hazmat suit in a drawer right outside the window of the decontamination airlock. This suit gives half the resistance of a regular suit.
If one's hacking skill is high enough, they can hack the security terminal, open the doors, then use the facilities terminal next to the sentry bot to disable the security system. Otherwise, when removing the agitator from the reactor, alarms will sound and the player character will have to deal with sentry bots, assaultrons, protectrons and automated turrets. With the Robotics Expert perk, one may also be able to hack the two protectrons beforehand.
Once the player character leaves the reactor area, they will find Brotherhood and Institute faction members fighting in the lobby. One can either leave immediately or choose to help the synths clear out the rest of the Brotherhood of Steel forces.
Speak with Allie Filmore again to complete the operation, then Father to start the next quest, Pinned.
- If one chooses to have Allie follow them, she will come equipped with a hooded cleanroom suit and an Institute pistol. She can neither sneak nor leave the Mass Fusion building and is essential for the duration of the quest. This provides fire support in the building, and she will also advise the player character on how to retrieve the agitator.
- Any active companion will join the player character in the Mass Fusion executive suite during this mission, despite none of them (save for X6-88) having any means of following them into the Institute and from there to the roof of the building. The sole exception is Danse, who will either be hostile at the next encounter as all Brotherhood members will, or if Blind Betrayal has been completed, leave for one of the settlements and thereafter be unable to be interacted with except for trading items and assignment to tasks/relocation to other settlements with the workshop menu (like an ordinary settler).
- Using the relay room to get to the Mass Fusion building makes The Brotherhood hostile. Alternatively, by informing The Brotherhood, Spoils of War will start, and boarding the vertibird that spawns on the Prydwen will make the Institute hostile. Every unfinished quest for one of the factions will fail immediately and they will permanently become enemies. This is the breaking point between the Brotherhood of Steel and the Institute.
- Completing this quest on the Institute's side, and thus becoming an enemy of the Brotherhood of Steel, is required to maintain one's cover and successfully complete the Railroad main quest line.
- If one has begun The Nuclear Option (Railroad) after completing Rockets' Red Glare, two Railroad agents will be standing on the roof when the player character relays to the normally inaccessible Mass Fusion executive suite, having been spawned for the sequence where the player character activates the detonator and destroys the Institute. If Allie is accompanying the player character, she will engage and kill them, but they will not engage her. The agents wear Mark I Railroad armor regardless of one's level.
- As of patch 1.2, it is impossible to inform Proctor Ingram of the Institute's plans while Tactical Thinking is active, thus making it impossible to start Spoils of War before completing Tactical Thinking and destroying the Railroad. If she is spoken to, she will simply direct the player character to Captain Kells.
- If Blind Betrayal has not been turned in to Elder Maxson, Tactical Thinking will not start. Thus, it is possible to start Spoils of War without finishing Tactical Thinking as long as that quest has not been added to the journal in the first place.
- Physically touching the agitator's housing with the player character's body while it is active will result in instant death.
Behind the scenesEdit
A beryllium initiator is used to generate neutron flux for starting nuclear fission reactions.
- pc ps4 xboxone The Sole Survivor can occasionally appear underneath of the rising elevator when taking it from the ground floor to the executive suite. [verified]
- A possible fix for PC users is to use tcl to get back onto the elevator.
- pc There is an occasion when using elevator to proceed down to the underground sector where the beryllium agitator is, Allie Filmore will appear in the elevator in the incapacitated state, even though she is at full health. This makes the situation become awkward as you have to proceed the quest alone from then on, to the last of the quest. [verification overdue]
- ps4 xboxone If you betray the Brotherhood of Steel and are their enemy prior to beginning this quest, then you may not be able to relay out of the Institute. Fast traveling to Mass Fusion does not fix this, and you must load a save from before you were enemies with the BoS. [verification overdue]
- pc Allie Filmore may become incapacitated during combat with the Brotherhood while heading down the building. As the Sole Survivor enters new areas, she will travel to them but will remained downed at the beginning of the area. She cannot be given a stimpak since there is only the option for dialog, and she will continue to speak as if she is moving with the Sole Survivor. Her body may even make it very difficult to exit the elevator without some fancy maneuvering. Despite this behavior, it is still possible to complete the quest, as Allie goes back to a normal state when she travels back to the Insititute. [verification overdue]