Restoring Order

Talk to Ada to relay what Jezebel has told you. Now you have to install an M-SAT mod to one of your robots. You don't need the Beacon now so you can have the M-SAT mod installed on Ada. Make your preparations and head to the Mechanist's Lair in the Robco Sales & Service Center, south of East Boston Police Station.

In the reception area, there's a Novice terminal and an advanced floor safe underneath it. You can use the terminal to unlock the safe. Go downstairs and grab the Robco Sales and Service Center Key on the filing cabinet to the north, beside the door leading back to the Commonwealth.

Loot the garage then have Ada (or the robot with the M-SAT installation) examine the strange device to reveal the hidden passage to the Mechanist's lair. Unlock the Advanced security gate by counter and get various ammo inside, including an Eyebot Model on top of the filing cabinet.

In the next hallway, there's a lot of laser tripwires that you can disarm manually (no components harvested). Since it's too much of a hassle, grab the fusion core from the active generator then look for an opening on the wall across it. The short tunnel will lead you to the Decontamination Control Terminal (Advanced) After successfully accessing it, select the “Decontamination Arch Control” and activate it. This will disable the laser tripwires. In the same room, there's an elevator that requires access to a Master-level terminal.

Proceed to the next room where the Mechanist will greet you using an Eyebot. Destroy it and all his robots in the room then order your companion robot to activate the access port to open the next room. There are no enemies here so proceed to the red door and continue down the ramp. Destroy more enemy bots that will attack you then continue forth. There are two quantum junkbots inside their pods. These are immediately hostile and can be released by using the Novice terminal on the table behind them. You can ignore them or deliberately activate them to gain extra EXP and robot components. You can also use the terminal to disable the turrets.

Head to the next room. There's a Robot Workbench beside a research terminal. And on the terminal is the remains of the chief engineer holding a Nuka-Cola Quantum. On his table, you can find a Mr. Handy Model and the Lead Engineer's Holotape.

Continue upstairs and take out more enemy robots. Proceed to the assembly line to encounter more quantum junkbots. Be careful of the two laser turrets in the other side of the room since they can easily rip you to shreds if your defenses are not enough. After clearing the room, be careful of the quantum tankbot that will be released from a hatch behind the retractable walkway. In the same hatch, you'll find a Weapons workbench.

After destroying it, go to the walkway and press the button to close the hatch and for the walkway to connect again. Cross the walkway and continue until you reach the next access port. Pick up all the loot in the room then order your robot companion to open the next security bulkheads. Head to the next access point and open it as well. Continue forth an another eyebot of the mechanist will confront you. Destroy it and two more junkbots to proceed. There's a Robot Workbench along the way as well. Continue down the flooded hallway then pick up the Robot Parts Model in one of the open lockers. Proceed and you'll find a power armor station beside the doorway. Use it if you need repairs to your power armor. Leave the room then turn left, press the red button to open the roll-up gate leading to the Parts Warehouse.

There are scrapbots that will activate only when you get near them, similar to feral ghouls playing possum. After clearing the warehouse, find the stairs to the NE corner and go up to the second level. Make your way to the lift and ride it to reach the other side of the warehouse. At the end of the corridor, you'll find another access port. Have Ada open it then continue to the next room. Another access port is waiting there so have Ada open it as well.

In the next room, you'll find a Mr. Gutsy Model under the table of the watch station. Beside it is the Forfeiture Terminal Password. Enter the red door beside the watch station table then go inside the property storage room. There's a Property Storage Lockup terminal where you can input that password. The lockup contains a lot of various ammo, some Weapons, a Robot Parts model, and many more. Take your time cleaning up the place. Leave the room and continue to the Research Labs and Holding Block A.

There are several dead feral ghouls locked up in the holding cells. Each cell has an Advanced lock and the loot from the dead ferals isn't that exceptional either. Go to the end of the hallway then take the stairs. On the tray below the medical observation terminal in the middle of the upper level of the holding block, you'll find a Protectron Model. Go back down then push the button on the side of the massive door to call in the large lift. Ride the lift down to continue.

Enter the Brain Extraction Room and grab the Robot Parts Model and Chief Scientist's holotape under the desk beside the Cerebral Conditioning Terminal. Aside from that, there's no interesting loot in the other rooms so continue west to the Robobrian Assembly and Incinerator areas.

In the incinerator area, there's a quantum robobrain that has a Medical Terminal password. There are also active scrapbots and turrets near it. The scrapbots will activate when you're near so it's much easier to target them in VATS and destroy them pre-emptively. Head to the assembly area. You'll come across another power armor station here and the Robobrain Production Terminal where you can use the password you acquired from the robobrain a short while ago. Proceed inside and activate the access port at the end of the path to continue.

Finally, you'll have to face the Mechanist. You have to fend yourself from the waves of various robots that will be sent your way. There's no special strategy needed here; just brute strength and firepower. If you have sufficiently upgraded Ada or your robot companion, it will be of immense help in this battle. Keep destroying the robots until the facility's power is drained.

Battle against the Mechanist's army

You'll also notice that the quality of robots the Mechanist will send you will diminish in quality, up to the point that you'll be dealing with easily-destroyed trashbots. Once the power of the facility has been drained, the Mechanist will finally talk to you. You can convince him to talk to you face to face in order to resolve the issue. You'll have the option to end the conversation in violence or be civil and let the mechanist atone for the sins comitted.

When you run out of robots to throw at the enemy

You'll receive the password from the Mechanist which you can use to disable the security alert in the mainframe. Once done, talk to Isabel (to start a new quest) and Ada to complete this quest.

Before leaving, check out Isabel's quarters right beside the command center to find a Drawing of the Mechanist on the desk, bobby pin box, a sentry bot model, and Mechanist's log holotape. Her room also has a red industrial trunk and cooking stove. On the work table, you can obtain the Eyebot Pod Schematics.

To the NW of her room, you can find another Robot Workbench, armor workbench, and Weapons workbench in the same room. There's a mini-nuke on the shelf in the corner and a Spotlight Schematic on the machine beside the robot workbench. Once you're done looting the place, you can use the elevator north of Isabel's quarters to go back up.

The Mechanist's Lair will have a map marker which you can use to fast-travel to the place. The lair is also a settlement so you can build structures in it and scrap the other junk to clean it up.