Mara was cast as the lead in the 2004 The WB pilot Prodigy, about a teenage child prodigy.[17] She had a recurring role on the WB's Jack & Bobby in 2005 and a five-episode arc on the Fox TV series 24 in 2006, playing computer analyst Shari Rothenberg. Mara joined the cast of the HBO comedy-drama Entourage for the series' sixth season in 2009. She played Brittany, Eric "E" Murphy (Kevin Connolly)'s assistant at his talent-management company and a potential love interest.[18] Mara filmed four episodes for the series in 2009.[19] In 2011, she guest starred on the FX horror series American Horror Story, as Hayden McClaine, a student who becomes Dr. Ben Harmon (Dylan McDermott)'s dead mistress, a spirit trapped in the Harmon house. Mara was offered the role by Ryan Murphy, her former producer on Nip/Tuck.[20]