Stewart's first starring role was at age 14 in the children's action-comedy Catch That Kid (2004), opposite Max Thieriot and Corbin Bleu. That year Stewart also played the role of Lila in the thriller, Undertow (2004). Stewart starred in the Lifetime/Showtime television film Speak (2004), based on the novel by the same name by Laurie Halse Anderson. Stewart, 13 at the time of filming, played a high school freshman, Melinda Sordino, who after being raped nearly stops speaking. Her performance was widely praised, with The New York Times stating "Ms. Stewart creates a convincing character full of pain and turmoil.