|Brotherhood of Steel main quest: Call to Arms|
|Speak to Paladin Danse.|
|Follow Paladin Danse to ArcJet Systems.|
|Follow Paladin Danse inside ArcJet Systems.|
|Speak to Paladin Danse.|
|Follow Paladin Danse.|
|Find a way to open the door.|
|Provide fire support for Paladin Danse.|
|Follow Paladin Danse to the ArcJet engine core room.|
|Restore auxiliary power to engine core.|
|Defeat the ambush.|
|(Optional) Activate the engine core's rocket.|
|Clear the control room.|
|Retrieve the deep range transmitter.|
|Exit ArcJet systems.|
|Speak to Paladin Danse.|
|Reward: 350+ XP|
Brotherhood of Steel membership
|Leads to: Semper Invicta|
Once one has agreed to assist Danse, he will order Scribe Haylen and Knight Rhys back into the police station. Follow them into the police station, where Danse offers the option to "resupply yourself" i.e. grab everything good in sight. After optionally talking to Scribe Haylen or Knight Rhys, tell Danse that you're ready to head out.
Follow Paladin Danse west to the abandoned ArcJet Systems building. Alternatively you can simply meet Danse at ArcJet Systems, but by doing so scripted encounters will likely be missed along the way, and along with them the opportunity for loot and XP. As Danse first reaches the river shore road, one will find a pile of ghoul and raider bodies which was not there before, along with two active frag mines. Then, a group of raiders will be found ambushing some traders under the railroad bridge: after the fireworks are over, the pack brahmin in particular usually contains excellent loot. Note that these bodies will all despawn as soon as the area is left, so the only chance to obtain this loot is during the trip to ArcJet. Further along, the Survivor may be attacked by various local dogs and insects before finally reaching the ArcJet building.
After a chat about the transmitter and automated security, provide fire support for the Paladin. He is dismayed to discover the presence of Institute synths. Head into the lab analysis room.
Here you have the option to: Hack (Advanced) into the lab control terminal or use the lab analyst's terminal to receive the lab control terminal password.
Use the lab control terminal to open the door, and the two of you will now begin fighting a way through numerous synths. When you reach the second floor corridor just outside the CEO's office, you can fight through the turret-lined hallway with Paladin Danse, or head into the server room nearby and use the terminal to disable them. Follow Paladin Danse to the elevator leading down to the ArcJet engine core.
Paladin Danse and you need to reach the top of the engine core in ArcJet Systems, but first you will have to search for a way to restore power to the access elevator. You can access the facilities terminal (Novice) and hack it. Start the auxiliary generators before returning to help Paladin Danse with his synth problem.
Alternatively you can press the Engine Start button on the Engine Core panel and watch the synths fry, noting that waiting longer before frying the synths will result in a higher body count for subsequent looting. Check on Paladin Danse, who will prove stunned but unhurt by the rocket blast, and then head to the elevator and ascend.
Battle to the control room and secure the Deep Range Transmitter off the corpse of a synth then leave the facility via the control room elevator. Outside, Danse will reward you with Righteous Authority and offer you the chance to join the Brotherhood. Whether you join or not at this time, he will subsequently be found back at the Cambridge Police Station, where additional quests can be obtained from him, Haylen, and Rhys if you do choose to join.
- It is possible to skip the entire first interior section of the ArcJet investigation by using a glitch to go immediately to the Engine Core. As soon as you enter the first hallway, you will notice a collapsed ceiling that appears to have blocked off the hallway to the left. You can actually jump through the small gap, continue around the corner and down the stairs to the right, and you will find yourself at the Engine Core door. This is a good way to save a lot of ammo and time if you don't feel like fighting a lot of synths. The quest continues normally.
- Another terminal can be found to the left of the locked terminal with the password inside if the player does not have the ability to hack advanced terminals.
- Copy of Tesla Magazine can be found upstairs next to the CEO's terminal.
- In the arc section, there is a segment of stair only accessible by falling from the top floor. Walking in triggers some synths to spawn. There is also a locked terminal which requires the ability to hack master level terminals and a Fat Man. (This section can also be reached by climbing onto the railing to the left of the doorway, and taking a running leap to the left.)
- In the maintenance wing off of the arc room, there is a Junk Jet on top of the table in the lighted room. There is also a holotape on the same table.
- There is an expert safe near the beginning of ArcJet that has a nearby terminal for unlocking it. You can unlock the safe with lockpicking, use the terminal to re-lock it, and continue this experience loop as long as you like.
- After you restore auxiliary power to the engine core you can hold off indefinitely helping Danse with the synths. As Danse is an essential character, the bodies will pile up allowing you to pocket a lot of fusion cells and Institute pistols. If left long enough fps may take a hit in that room but if you activate the engines many of the bodies will be reduced to ash piles solving this. Saving and reloading after activating the engines may cause the loot in these ash piles to be inaccessible so be sure to collect it all before moving on.
- If you have already completed Institutionalized and have not alienated the Institute, most of the synths will be non-hostile, only ever attacking Danse as you travel through the factory. The one exception is the first group that ambushes the player, which will always be hostile.
- The quest can be started without Danse by entering the Engine Core, starting with the 'proceed to the control room' stage.
- Deactivating the turrets before Danse destroys them all will make him just stand around. To solve this, either reactivate them so Danse destroys them to proceed ; Destroy them while they are deactivated or simply continue to follow the objective and once you're past this hallway, Danse will resume on his path.
- pc After Paladin Danse notes that there are turrets up ahead, he might turn around and head back in the direction you came, eventually coming to a stop and not moving at all. To get the quest to progress, destroy the turrets, and Danse will resume heading in the direction he is supposed to. [verified]
- pc When Paladin Danse reaches Arcjet Systems, before entering he may run back to the Police Station. Once there he will stand in front of it and will not talk. However if you continue the quest normally (albeit without danse), he will teleport to you at the end and the quest can be finished as normal.[verified]
- pc If this quest is not completed before Reunions and the Prydwen shows up, it will trigger a glitch that not all Brotherhood vertibirds and patrols will spawn correctly. [verified]
- pc After you finish the quest and head into the service elevator, the elevator door might not open, leaving you stuck in there. [verified]
- pc This can be fixed with the console command CompleteQuest 001a7bd2. Note that this may cause excessive lag afterwards, in which case, use the console command PCB.
- pc When trying to leave ArcJet through the elevator, you might get a CTD. Reloading a save doesn't help and you are stuck here. To get out, use console command coc ArcJetSystemsExt02. Once out, enter in the bunker and go to open the elevator doors, just like if you get out of it. Paladin Danse will pop and the quest will continue normally.
- pc The terminal found in the room with the Fat Man is mislabeled as an Expert level hack, when in reality it is a Master level. [verified]
- pc If you enter the control room with tcl while not having the quest active, you start the quest and your companions are stuck there (or they will walk to the control room). There's no fix for it at this moment. [verified]
- pc If the Brotherhood has been destroyed, the quest will be impossible to complete, as you will not be able finish the quest by speaking to Danse. This can be fixed with CompleteQuest 0006f5c1.[verified]