This guide will help you complete the Institute Quest: Mass Fusion in Fallout 4. Things are getting heated between the factions, and it’s time for you to determine where your loyalties lie. If you’re ready to follow through with the Institute’s plans, complete each step in this guide to help them in their endeavors.
Speak with Allie Filmore
- Relay to Mass Fusion
- OR Inform the Brotherhood
After chatting with Father at the end of the previous quest Mankind Redefined, head down to the main level of the Institute to locate Allie Filmore. Speak with her about an upcoming operation that she expects you to lead. Allie asks you to retrieve an item called a Beryllium Agitator from the Mass Fusion building.
At this point, you have a choice to make regarding which faction you choose to support. If you would like to continue working with the Institute, then decide whether or not to allow Allie to join you for this mission, then relay to the Mass Fusion building. This will make you a permanent enemy to the Brotherhood of Steel, and will cause several of their quests to fail.
If you would rather cut your ties with the Institute instead, then exit the Institute and visit the Brotherhood of Steel. Informing them of the Institute’s plans will officially swap your loyalty over to the Brotherhood, and the Brotherhood of Steel Quest: Spoils of War will commence.
Locate the Beryllium Agitator
Assuming you have decided to stick with the Institute, choose whether or not to bring along Allie Filmore, then fast-travel to the Mass Fusion building using the Relay on the upper level. The mission ahead involves heavily armored enemies and exposure to radiation, so prepare yourself accordingly by bringing healing supplies. Consider wearing your Power Armor suit as well, if you have it available.
Retrieve the Executive Keycard
When you arrive on the rooftop of Mass Fusion, prepare to combat the enemy forces that have already infiltrated the building. Eliminate the hostiles, then go one level down into the executive offices. Look for a desk along the balcony, in front of a large Mass Fusion sign on the wall. Collect the Mass Fusion Executive Lab Password, as well as the Mass Fusion Executive ID card from the desk.
Enter the doorway along the northwest wall, adjacent to the desk that you just rummaged through. Head left toward the Executive Research Lab Terminal along the far wall, and use the password you acquired earlier to access the blue terminal. Select and read each of the personal intramails to learn the location of the Agitator.
Proceed to the Reactor Level
- Optional: Restore Power to the Elevator
Enter the large cylindrical elevator in the center of the chamber, and slide the Mass Fusion Executive ID card through the ID card reader to activate the elevator. As you ride the elevator down to the lower level, fire a few shots at enemies that try to harass you along the way.
Part way down, your elevator will run into a slight hiccup. To reach the Reactor Level, you must either restore power to the elevator, or find a way to trek down to the lower level on foot. Restoring power to the elevator is the better option here, and you have two ways to make it happen.
First, exit the elevator and eliminate any hostiles nearby. Then, locate a computer terminal in an office west of the elevator on the same floor. If you have upgraded your Hacker perk to unlock Expert level terminals, then you can hack the Development Manager’s Terminal to restore power to the facility.
If Expert hacking isn’t available to you, then you can search for the circuit breaker instead. Enter the doorway northwest of the elevator, and pass through several more doors to reach a room on the second level. You should see a breaker box on the wall just past another door ahead. Open the breaker box and activate the circuit breaker, then head back to the elevator to continue your trek downwards.
Retrieve the Beryllium Agitator
Once you reach the Reactor Level, continue down the stairs through each chamber to reach the main lab just before the Reactor room. Be sure to loot the area for Stimpaks, RadAway, a Hazmat suit, and other useful supplies before entering the Reactor chamber.
When ready, enter the eastern hallway and press the decontamination button. Wait for the decontamination sequence to complete, then proceed through the next door into the Reactor Chamber.
Unlock the Reactor
Walk along the metal walkway to reach the Reactor. Press the Interlock Release button in front of the Reactor to unlock it.
Take the Beryllium Agitator
After unlocking the Reactor, remove the Beryllium Agitator, then prepare to quickly leave the chamber. Exit through the same door you entered from, initiating the decontamination sequence once more to unlock the door to the lab.
Eliminate Reactor Level Security
Stealing the Beryllium Agitator causes the facility's defense system to activate. A Sentry Bot and a Protectron will attack your position as you enter the lab room. If you have a Fat Man or any other heavy firepower, now is a good time to put them to use.
Eliminate the pair of defensive robots, then use your ID card to open the main door to leave the room. As you pass through the main door, prepare to face a pair of Assaultrons. Take down the bots, then proceed toward the exit. Watch out for laser turrets, machine gun turrets, and another Protectron on your way out.
Exit Mass Fusion
- Optional: Assist Institute Forces in the Lobby
After you have eliminated the security defenses, backtrack through the corridors until you reach an elevator labeled with an Exit sign. Ride the elevator to the main lobby.
As you exit the elevator, you find your fellow Institute reinforcements being attacked by enemies. You can optionally aid your Institute commrades and help them defeat the enemies in the lobby, or you can simply exit the building instead. When ready, exit through the door to the Financial District to leave the Mass Fusion building.
Speak to Allie Filmore
Use your Pip-boy to Relay back to the Institute. Locate Allie Filmore, and speak with her about the outcome of the operation. Once you give her the Beryllium Agitator, the quest concludes, and the Institute Quest: Pinned will begin.