Theatrical Trailer for Flashback, starring Dylan O'Brien, Maika Monroe, Keir Gilchrist, Hannah Gross and Emory Cohen.br br Frederick Fitzell (Dylan O'Brien) is living his best life -- until he starts having horrific visions of Cindy (Maika Monroe), a girl who vanished in high school. He reaches out to old friends with whom he used to take a mystery drug called Mercury, but realizes the only solution lies deep within his own memories. So Frederick goes on a terrifying mental odyssey to learn the truth.