1. When you receive the quest in the Drain for the basement at the inn in the Wachter Estate, it is designated as Grubby Missives for the Gentleman. If you try to give it to the Gentleman, however, there is no option to do so. He also says he may have work for you in the future, but not now. Who you really need to give it to is one of the three Shady Looking Men, who will also offer a return quest for the Drain.
2. The return quest is the Slaving Accounts, but it has "Unrecognized Token" in the text.