Caitlin's family adopted Simon, a Korean boy, just before Caitlin's father left their family. Caitlin thinks she, her mother, and Simon form a perfect family. But when Simon's older sister, Youn Hee, turns up in a Korean orphanage, Caitlin agrees that adopting her is the right thing to do, and she's sure it will be fun to have a sister her age. But when Youn Hee joins the family, Caitlin learns it's rewarding, but not easy, to have a new sister.