Someone is trying to blackmail a local lord. The blackmailer apparently has proof of some of the lord’s past… indiscretions. If that got out, it could ruin the lord politically (a fate worse than death to him). What the lord needs is a group of discreet adventurers to locate and “deal” with the blackmailer. The lord will tell the PCs about the notes, and who he suspects the blackmailer is (a political rival). Then he leaves the whole mess in the PCs hands.
The blackmailer has apparently found an illegitimate child of the lord, and is threatening to introduce her as such. Therefore the PCs must track down both the blackmailer and the child.
The rival is the blackmailer. However the PCs track him down, they still have to find the girl. Her name is Gypsy, and she lives in whatever city is most convenient. Now, once the PCs start figuring things out, it gets really confusing.
Gypsy is not the illegitimate daughter of the lord. She is actually his estranged, run-away legitimate daughter. When she left home, there was an unspoken agreement that they would pretend that she was not connected to the family in any way. She doesn’t acknowledge her father because she can’t stand him, and he doesn’t acknowledge her because she’s a disgrace to him. The rival, who did not know this story, met Gypsy once in the city, and noticed the family resemblace. He made the logical conclusion from the information he had. Gypsy does not know of the blackmail plot, but she would approve of it. She would not help the rival with it though. It will be very hard to convince her to help the PCs straighten things out. Assuming they do get things straightened out, the lord will, of course, try to stiff them.