Boston After Dark

Boston After Dark is a Railroad side quest in Fallout 4.

Detailed walkthrough
Dr. Carrington asks the Sole Survivor to assist with the newest rescued synth.

Find the message from Old Man Stockton in a mailbox first or head directly to Bunker Hill and talk to Old Man Stockton inside the building. He'll respond to the security phrase with the information: that there are raiders at the drop-off location and asks the Sole Survivor to clear the area. Passing speech checks can get more caps and/or the first mention of "Patriot".

Head to the church that's indicated by the quest marker and kill the raiders, then wait until it's night time. Stockton will bring the synth named H2-22, and give the all clear sign by lighting a lamp in the window, then he leaves. Talking to the synth doesn't reveal much information, since he's been told not to talk to anyone. Passing increasingly harder speech checks reveals that he's been a maintenance worker at The Institute, and has been treated no better than a tool.

After some time, a Railroad operative called High Rise arrives and after a brief talk, he tells the player the way to the safehouse has Raiders around the area. The Sole Survivor and High Rise will then proceed forward with H2, fighting through the Raider outpost. Upon reaching Ticonderoga, they will thank the Sole Survivor for the assistance, and the location will be usable as a safehouse from then on. Speaking to the synth reveals he's scared, but hopeful about his future.

Return to Carrington to receive a reward and the next mission.

Bugs

 * If you head to the church to "secure the rendezvous" and the raiders are dealt with, Stockton may not arrive, leaving the quest unable to be completed.
 * Upon arriving at the church, you may discover two raiders inside and one feral ghoul outside (or already killed by two raiders). After killing the raiders and ghoul, the quest still may not progress and your objective will remain "Secure the rendezvous point." The quest requires that you kill three raiders to advance to the next stage and the ghoul mistakenly spawns in place of a raider. This bug makes it impossible to complete the quest on Xbox. On PC you could use console to resurrect and kill again one of the raiders and quest will move to next stage as expected.
 * If you wait in the church until night time by sitting on one of the pews, old man Stockton will arrive and address you to H2-22, but H2-22 will not be present in the area and the option to speak to Stockton is unavailable. A possible fix is traveling to a close area and running back to the church, you can speak to Stockton again after this.
 * It's possible to pick up the Augusta report and start Butcher's Bill before reporting back to Carrington. If you complete Butcher's Bill as well, you can no longer hand in Boston after Dark. Carrington will only have his generic dialog. The quest can seemingly only completed via the console with.
 * Stockton and H2-22 may also arrive during daytime.