Flashback (2020)

"Flashback" is a 2020 Thriller movie directed by Morgan Emmery and starring by Dylan O'Brien, Hannah Gross. Frederick Fitzell is living his best life—until he starts having horrific visions of Cindy, a girl who vanished in high school. After reaching out to old friends with whom he used to take a mystery drug called Mercury, Fredrick realizes the only way to stop the visions lies deep within his own memories, so he embarks on a terrifying mental odyssey to learn the truth.