Jewel of the Commonwealth Main Story Quest

1. Go to Diamond City

The Diamond City should be marked on your pip-boy map.

Diamond City is the largest settlement in the Commonwealth. It's the best place to begin the search for Shaun.

Talk to Piper waiting outside closed Diamond City gates.

Inside you can talk to the mayor McDonough and Piper or go directly to the market.

Either way you will get a new quest - Story of the Century.

2. Find Information about Shaun

Talk to Moe Cronin. Persuade or bribe him, then he will direct you to the Valentine Detective Agency. You can skip this stage and go directly to the Nick Valentine's Agency.

3. Go to Valentine's Detective Agency

I've discovered that Diamond City is the home of a detective, Nick Valentine. He might be able to help me find Shaun.

Go to the agency and talk to Ellie Perkins. The detective is missing so offer her your help in finding Nick Valentine.

4. Quest Completed

I need to find Nick Valentine, the detective who could help me locate Shaun. Nick was last seen heading to Park Street Station on a case.

Next / new quest is Unlikely Valentine (Main Story).