This quest has changed with the Wastelanders update. Once you leave the Vault, talk to the Mr. Handy (Pennington) by the "Vault-Tec Celebrates 300 Years Of America" arch, and he will ask you to make sure the two women standing a short distance away aren't up to anything. Talk to them to learn about a new tavern called the Wayward, and a marker will be added to your map with the quest "Wayward Souls". Head to the Wayward and go inside, where you can watch what happens next or attempt to intervene. Once you're able to talk to Duchess, ask her about the Overseer at some point in your conversation (I did this last after picking up her quest chain), and you'll start "First Contact". From there it's just a matter of following the instructions to finish the quest.