Twelve-year-old Sarah Willis sees another version of herself in the mirror living a (totally weird) parallel life. As she grows older, she becomes dissatisfied with her mundane, academic life and envious of the wonderfully reckless, daring, and theatrical experiences Other Sarah has. Risking her reputable teaching career and last shred of dignity, Sarah seeks to make the two women's lives converge by developing relationships with the counterparts of Other Sarah's friends and family in her world. When she gets overly invested in Other Sarah's ex and his children, Sarah's decisions threaten to tear both women's worlds apart. Faced with losing the only life she's ever actually lived, can Sarah make things right and give up the dream of living her other life?