Restoring Order

Restoring Order is a quest and achievement/trophy in the Fallout 4 add-on Automatron.

Detailed walkthrough
The Sole Survivor is tasked with finding and stopping the Mechanist once and for all. They go to the RobCo sales and service center where The Mechanist's lair is hidden. Once inside, the player must get their robot to use the M-SAT on several devices stuck to walls to open the blast proof doors throughout the lair. After a lot of battling, the player will finally make it into the Mechanist's war room. Inside, they will battle several waves of increasingly tough robots, the last one being a Dualbot. Once it is killed, the power will fail and a speech check will allow the player to make the Mechanist stand down. (The dialog here is timed, if you wait too long to speak with the Mechanist, she will turn hostile.) After explaining herself, the Mechanist will take off her helmet, revealing herself to be Isabel Cruz. She will then thank the Sole Survivor, before giving them her costume and walking away. She will usually also give the side quest Rogue Robot. Ada will also thank the Sole Survivor and once this is over, the quest line and main story of Automatron completes.

Bugs

 * After the power fails, the Mechanist may not speak with you, making the quest impossible to complete. Loading a save before the battle starts may fix the problem.

After the 1st wave of robots, the Mechanist will start a dialog with "Look around you" and the assembly lines on the ceiling will start carrying robots around, DO NOT shoot them while they are in this stage. It's highly possible this is the reason why dialog does not start as it should be and the battle will lock in never ending frag mines and fuel tanks raining on player.
 * Wearing power armor with a Targeting HUD mod may make the Mechanist & Sparks become hostile towards you. Removing the mod or the entire helmet or exiting your power armor can fix this..