If you love "The Sound of Music" and "Pride and Prejudice," prepare to be enchanted by "Must've Done Something Good!" Sylvie O'Rourke, "The Sound of Music" devotee and born procrastinator, is about to die. Well, she thinks she is, anyway, and so attempts a last-ditch bargain with God for her life. "You guys are my witnesses," she tells her sisters somewhere over Connecticut. "If we get out of this plane alive, I promise to do something good with my life." Back on firm ground, Kate and Meg won't let their sister forget her promise, and with their years of practice hitting just the right chords of guilt ("What kind of person lies to God?" Meg wants to know), Sylvie finally caves. A teaching position at the broken-down St. Matthew's High School appears to be Sylvie's perfect opportunity to do some good. That is, until she's snubbed by a fellow teacher on the first day of school. Whether she's becoming a bit too invested in the students' fall fundraiser or directing the school's sure-fire musical disaster, Sylvie's charmingly irreverent style gets her called down to the principal more often than her students. Can Sylvie keep her promise and make it through the year, dignity and sanity intact?