The Secret of Cabot House

The Secret of Cabot House is a quest in Fallout 4.

Quick walkthrough

 * 1) Complete missions Special Delivery and Emogene Takes a Lover, before this mission becomes available.
 * 2) Talk to Jack at Cabot House.
 * 3) Meet Jack outside of Parsons State Insane Asylum.
 * 4) Help Jack reach his office.
 * 5) Help Jack reach the basement.
 * 6) Stop the raiders from freeing Lorenzo Cabot.
 * 7) Kill or free Lorenzo Cabot.


 * Plan A: Killing Lorenzo
 * 1) There are four switches in the room you have to activate. Once you do so, Jack will finish him off.
 * 2) Return to Cabot House in a week to further the mission.


 * Plan B1: Setting Lorenzo free
 * 1) Talk to Lorenzo Cabot
 * 2) Return to Cabot House
 * 3) Talk to Jack Cabot
 * 4) Criticize Jack Cabot
 * 5) Kill the Cabots
 * 6) Talk to Lorenzo Cabot


 * Plan B2: Killing Lorenzo, part 2
 * 1) Talk to Lorenzo Cabot
 * 2) Return to Cabot House
 * 3) Talk to Jack Cabot
 * 4) Apologize to Jack Cabot
 * 5) Kill Lorenzo
 * 6) Talk to Jack

Detailed walkthrough
When returning to the Cabot house after saving Jack's sister, the player character will get this mission assigned by Jack to help prevent raiders from freeing Lorenzo. Although one can actually fail in preventing the raiders from freeing Lorenzo, the Sole Survivor still has to kill them all once Lorenzo is released.

OR
 * Upon flipping the switches and killing Lorenzo, Jack tells you Lorenzo would have killed his family as well as the player. He says his family influence was the only thing keeping his father in the asylum as opposed to Death Row due to his crimes during his life. Jack says that now that the world is "built for monsters", nothing would have stopped his father from presumably returning to criminal activity. You can choose to thank him or berate him for being sad only because he "lost [his] mortality juice"; though Jack seems to genuinely believe he could have removed the artifact and cured his father with a little more research. He awards you with about 500 caps and tells you to return to his home in about a week. He gives you a slightly different amount of caps depending on what you say following killing his father.
 * When an in-game week has passed, you will receive a notification that tells you to visit Jack back at the asylum. He tells you he figured out how to access the telekinesis effect of the artifact. He gives you Lorenzo's Artifact Gun.


 * Choosing to save Lorenzo by pushing the switch by his door will prompt Lorenzo to leave his cell; him saying he wants to have a "long overdue" conversation with his son. He tells you "we'll have to kill him, you know. And the rest of them." He tells you his son trapped him in there in 1898; nearly 400 years before the in-game date.
 * Arriving to Cabot house, Jack will ask why you freed him. The next conversation options will allow you to either help Jack further by saying you can help him, or help Lorenzo by saying he is wrong and then killing the Cabots. Whatever you choose to say, Lorenzo will appear on the balcony overlooking the family room. Wilhelmina tries to sell Jack out by saying she would never allow him to do what he did, but Lorenzo berates the family for feeding on his blood. Lorenzo then turns hostile to the Cabots (and the Lone Survivor if that option is chosen).
 * After killing him, Jack will reward you 502 caps, saying he no longer needs your services. Every quote from him following quests' end either mourns his lost family or berates you for not listening to him.
 * Otherwise, after killing the Cabot family, Lorenzo will offer a "lifetime supply" of Mysterious serum, i.e., one at a time, which cannot be sold or traded away.

Bugs

 * Jack Cabot sometimes spawns on the other side of the unpickable door leading to Lorenzo in the basement, preventing the quest from proceeding.
 * It can be fixed by forcing the door to open (with console command "unlock") and when Jack gets back to the player then closing the door (with console command "lock").
 * Completing the quest in Jack's favor may incorrectly display the quest completion text in the Pip-Boy as if you helped Lorenzo. This does not seem to affect earning the artifact gun reward.

Тайна дома Кэботов