It's springtime in suburban Rosewood, which means iced soy lattes, fresh manicures in shimmering pastels—and prom. But while everyone else is flipping through the racks at Saks in search of the perfect dress, Hanna, Spencer, Emily, and Aria are on a different kind of hunt: They're looking for A. . . . Hanna puts her campaign for prom queen on the back burner to volunteer at the burn clinic, whe...