After you save your sister and the two other little girls, go to Windfall island at night. The poor guy's daughter will be rich and the rich guys daughter will be poor. Go around the island until you find the used-to-be-rich girl. She will tell you to go away and motion her head to the side. Go in that direction. She will run away. Watch her for a while, but don't be seen. If you are and she runs away and the screen goes black, go into a building and come out again. If you keep following the girl, she will go into a shop. The shop of the guy who gave you a sail. She will be stealing his money. She will ask you some questions. Always choose the option on the top. She will thank you for stopping her from being a theif and will give you a bottle. (Oh joy, another one)