- Talk with Deacon
- Meet Deacon at the old highway
- Follow Deacon and find the "tourist"
- Talk to Deacon
- Get inside the escape tunnel
- (Optional) Enter base through front entrance
- Get Carrington's Prototype
- Leave the Switchboard
- Meet Deacon at the Old North Church
- Talk to Desdemona
- Follow Desdemona
Speak with Deacon at Old North Church for your next mission with The Railroad. He will send you to Lexington. Leave via the escape tunnel and unchain the door so you may reenter through this route. Head towards Lexington and meet up with Deacon.
Deacon will ask you to get some info from someone called "tourist", a man by the name of Ricky Dalton. Meet up with him a give him the Railroad password. There are a variety of dialogue options you can have with Dalton here.
Dalton will inform you that the old base known as the Switchboard is overrun by Synth enemies. You can enter via 2 ways, the back sewer entrance or enterring via the basement of Slocum Joe's. However, going through the basement is much more difficult and the elevator at the end is not operable as of yet. Go back down the collapsed highway and follow the Pip-Boy marker to the the tunnel entrance, which is a sewer drainpipe. Make sure Deacon is with you to override the locked terminal.
Make your way through the sewer until you get to the Switchboard, Deacon will open up doors as you progress. His pathing is a little buggy during the quest, so you may need to save and reload to get him to progress at times. At the target room, Deacon will access the terminal and open the security door to obtain Carrington's Prototype. Leave to Lexington being mindful of the Fragmentation Mine buffet laid out on the streets right near here. Use VATS to target and eliminate them all. Return to Old North Church and speak to Desdemona. She will confer upon you a codename of your choosing or call you "The Wanderer" if you do not choose. At this point, the misc Railroad quest Boston After Dark becomes available. She will welcome you into the headquarters and eventually will ask you to leave your current Faction and join The Railroad. You may accept, reject or delay the choice.