How to unlock: After saving Nick Valentine during the Unlikely Valentine main quest, you must visit his detective agency in Diamond City (M6,1) and check his investigation files of Earl Sterling.
- Look for some tracks in Earl Sterling house
- (Optional) Obtain the key to Earl Sterling's house
- Investigate the Mega surgery center
- Investigate hospital basement
- (Optional) Obtain the key to hospital basement
- Speak to Ellie
Unlock the investigation
You can start this quest after you save Nick Valentine during the main storyline of the game. Once you do it, you must go back to Diamond City Market and to Valentine Detective Agency. After you enter the building, you must find Earl Sterling's Case File that is lying on one of the desks. The quest will officially start and will be added to your journal after you check the files and listen to the commentary made by Ellie Perkins.
Important - During this quest you don't have to travel with Nick, but if you take him with you, you will hear many of his comments.
Finding some tracks in Earl Sterling's house
Earl Sterling's House can be found in the Diamond City Market. If you have adequate skills, you can try using the pin to open the door, but such action will be considered as breaking in, so it is wise to be stealthy and to avoid being detected while trying to open the door. Another way is obtaining the key to the house. In order to do it, you can visit Dugout Inn. Once you get there, talk with Vadim who is the owner and ask him for Earl Sterling's House Key. You will receive it without having to use persuasion or other advanced means.
Once you use the key or break in, start exploring Sterling's house. Take interest in the Surgery Receipt shown on the picture above, it is lying next to the coach. Checking it will point your investigation towards the local clinic.
Examine the Mega surgery center
Leave Sterling's house and find Mega surgery center where doctor Sun is working (only during day). Talk with him about Earl Sterling. If you have developed your Charisma enough, you can start the topic of the receipt you found and then talk about doctor Crocker. Later in the conversation talk about obtaining access to the basement of the clinic - you can bribe Sun with 100 bottlecaps or use Charisma to intimidate him or convince him that you are looking for a missing person.
Investigate the basement of the hospital
The easiest way for obtaining the Surgery Cellar Key is by successful conversation with doctor Sun (bribe, using persuasion). Another way of obtaining it is pick pocketing.
If you don't want to or can't obtain the key that opens the hatch to the basement, you can also use bobby pins. However, make sure that you will not be caught red handed.
In the basement you will meet Doctor Crocker. The encounter can end in two ways. If you have high Charisma, you can select one of two dialogue options related to convincing Crocker to resign on further actions. In both cases Crocker will commit suicide. If you will lead the conversation in aggressive way or if the persuasion attempt will fail, the battle will start. Luckily, Crocker isn't a hard opponent to defeat.
No matter how you acted, you can search the body of Crocker (you will find the key to his apartment and other items). Talk to doctor Sun in order to tell him what happened and go back to the detective agency. Report to Ellie Perkins.
Quest rewards: Experience points, bottlecaps.