How to unlock: The quest will start automatically in the Museum of Freedom (M1,2) during the When Freedom Calls main quest.
- Go to Diamond City
- Obtain information about Shaun
- Go to Valentine's Detective Agency
Journey to Diamond City
You can unlock this quest during the final part of the When freedom calls main quest. After the large battle with raiders and deathclaw in the Concord city, you will have to return to the Museum of Freedom. There, talk with Preston Garvey and with Mama Murphy. You will be sent to the Diamond City in search for kidnapped son. The city is far south from your current location. On the way you can be attacked by bandits or monsters, but the city itself is protected by neutral guards and you don't need to be afraid of their attacks. Boards with directions will lead you to the entrance to the city.
Obtaining information about Shaun
Get close to the closed gate leading to the city and talk with the reporter named Piper who can be found here. She will help you get inside. Now, meet with mayor McDonough. If you have Charisma developed, during the conversation with the mayor you can pick a unique dialogue option and be pointed straight to Valentine's detective agency. Otherwise, talk with any person in Diamond City and you will be pointed to the agency.
Visiting Valentine's detective agency
Use the passage leading to Diamond City Market. Go to the back of the location and explore the narrow alleys. You will find the entrance to Valentine's detective agency. Talk with Ellie Perkins inside, she will tell you that Valentine has gone missing. During the conversation you can use dialogue option related to high Charisma twice, first time to tell her that you have an important business with the detective, and then to encourage the woman to put a price (125 bottlecaps) for finding him. No matter how you acted, the quest will end and another one will start, related to finding Valentine.
Quest rewards: Experience points, new main quest (Unlikely Valentine).