After exploring the Diamond city and talking to the Detective's secretary Ellie Perkins, it's time continue with the further main story quest to locate Nick Valentine and discover the new Vault 114 along with few more looting and get grip of the weapons and combat systems of the game in this Fallout 4 Walkthrough Part 4: Unlucky Valentine.
Now be sure you climb upstairs and grab the First Aid box from the dresser to the east. Exit the Building and let's begin with our hunt for Nick Valentine. You need to head towards the Park Street Station from the Diamond City and on your way you will encounter threats and foes as the road ends, keep moving towards the north-east and take down the Raider on your way towards the Trinity Plaza.
Take right from the Trinity Church and you'll come across the fountain to your left and you'll, however, complete the first step in the new road to Freedom quest(Later in the game). later you'll come across the Park Station Gate and enter the Blue Double doors to continue your investigation for Nick Valentine. Now crouch, stay in hidden mode until you reach the broken escalator and notice few bad guys which you are about to take down. Kill the first guy headshot to get the damage bonus.
Now the other guys will be heading towards you and try to take you down, but if you want to take zero damage we have the best strategy to kill them all with taking any damage. First backup yourself up the escalator and kill any guy who goes through the door, you can also throw some Molotov for getting massive kills. Once the area is clear and good to go, head to the rooms and grab anything useful and get ready for some more action.
The area you will be traveling is quite narrow and easy to take down the enemies when hidden. The Route to the Vault 114 is not easy, but it can be if you try to deal with these guys in a tactical aspect. As you move forward you need to head downstairs and deal with some more enemies and move ahead another pair of enemies are waiting for us. You need to follow the same tactics to deal with these guys and before you start eliminating them make sure you Quick save the game.
Now you are at the Entrance of the Vault 114, and get ready to deal with a pair of guards once you're inside the Vault. Then head down where you'll hear few guys having a conversation about the vault, aim at one of the bad guys and try to take a headshot for an extra bonus. Head straight until you come across an area with stairs and enemies nearby, so first clear the area, head left and you will see a room with a hole/open hatch in the floor.
Before you jump down to make sure you take the bad guy with a headshot or a Molotov, then move forward to the next section where you'll come across a chamber on the third floor where a Mobster and Valentine are having a conversation. Make your waypoint locate Nick Valentine, but before that you need to take the Mobster and grab the Overseer Door Password.
Use the Terminal to override the door and make sure it should be open when your exit, find Nike Valentine inside the Room with Speech Bobblehead on the desk which can be used to get 100 more caps from the Diamond City Vendors. Begin with the conversation with Nick and try not to mess up with the conversation. What we did is informed him about Shaun and later get our next objective to get back out of the Vault.
From now just keep following the Detective Valentine, where he will take you downstairs and a bunch of Bad boys are waiting for us. Here you can either sneak quietly or just begin with the Killing it's all up to your playing style. If you are done killing then don't forget to take the necessary items by looting the dead bodies, continue following Nike.
Nike will take you through the doors which were previously looked and later you'll encounter few guards, so take them down and make sure you don't miss any door which has locks as they have unique and various different collectibles in it. Once you have climbed the stairs a nurse on the left and an advanced locked door on the right which should now be easily opened with your skills. Here you will find some caps and goodies.
Continuing with Valentine towards another locked door, luckily the synth had saved us this time. Once you get inside, we will be greeted wit the Mob Boss and his cohorts, try tot talk to them and make sure you end up the conversation by letting the women leave. Once this is done you and Nick head out of the vault and then to the Park Street Station. At the back Bay ladder, climb up to the city's surface and inform Nick that Ellie has sent you here.
Now that you have gained his trust he will offer you to join him at his office and discuss in detail about your missing son, so simply agree with Nick to follow him back to the Diamond City and thus concluding the Main Mission 4: Unlucky Valentine.