Tradecraft Main Story, The Railroad Quest
This quest will be triggered or can be aquired when you complete Road to Freedom quest.
Related points of interest
Stages of "Tradecraft" quest
1. Talk with Deacon
If I want to have more dealings with the Railroad, I should talk with Deacon. He's the mysterious man who vouched for me when I met with Desdemona, the Railroad's leader.
2. Meet Deacon at the old highway
Deacon wants to help me join the Railroad. In order to join, I have to help him on a mission. He said he'd meet me by the old freeway outside Lexington.
3. Follow Deacon and find the "tourist"
The Railroad's old base is near Lexington. Before we go inside, Deacon wants to get information from someone who's helping the Railroad - a "tourist." So it's time to follow Deacon.
Follow him, then talk to Ricky Dalton. The password is "Mine is in the shop".
5. Get inside the escape tunnel
The Railroad's old base is crawling with older model Synths. Deacon suggests we use the back entrance to get inside and complete this mysterious errand we're on.
5.1. (Optional) Enter base through front entrance
You can't use it becouse the elevator is not powered up so you are forced to use escape tunnel.
6. Get Carrington's Prototype
Somewhere inside the Railroad's old base is a prototype that a Doctor Carrington needs. Deacon says we can expect serious resistance from "Gen 1" and "Gen 2" Synths.
The first terminal inside the sewers is master-locked but Deacon can hack it for you, just talk to him.
Travel through the tunnels and rooms of the Switchboard.
You will find Power Core Generator in a small room adjacent to the main control room. There is also an issue of U.S. Covert Operations Manual magazine on the desk inside the main control room.
In the end you get to the door that resembles a giant safe. Let Deacon open the door, Carrington's Prototype is on the shelf inside.
There is a body of Tommy Whispers lying on the ground. Deacon will take and give you his weapon - Deliverer.
7. Leave The Switchboard
Now that we've recovered the prototype from the Switchboard, it's time to return it to Desdemona. She'll be at the meeting place underneath the Old North Church.
Go to the room with elevator, use terminal to power it up, use elevator, move bookcase blocking an exit and go outside.
9. Quest completed.
I impressed Desdemona enough with my actions at Switchboard that she asked me to join the Railroad.
You are now a member of The Railroad and Deacon can be your companion.
Next / new quest is Boston After Dark (Main Story, The Railroad).