Flashback

In FLASHBACK Fred Fitzell (Dylan O'Brien), on first glance, appears to have his act together. He's starting a job in the lucrative field of data analytics, is moving into a nice apartment with his long-time partner Karen (Hannah Gross), and is settling into a comfortable adulthood, even if his dreams of being a successful visual artist are now on the backburner, and his mother is in the hospital suffering from aphasia and no longer recognizes him. But on a traffic-heavy commute home from work, Fred tries to take a shortcut through an alley, and sees and/or hallucinates a homeless man who triggers hazy and unpleasant memories from his past. Specifically, he begins having recollections of a girl he knew in high school named Cindy Williams (Maika Monroe), who mysteriously disappeared on the night before their final exams while Fred, Cindy, and their friends Andre and a drug dealer named Sebastian experienced disturbing hallucinations and freaked out while on a mysterious designer drug known as "Mercury." He recalls Cindy as being a free-spirited rebel, and soon becomes obsessed with figuring out what really happened to her 15 later. Fred tracks down Sebastian and Andre, and the three of them begin trying to piece together what exactly happened on the night of Cindy's disappearance, and they soon revisit the abandoned building that was the drug house where, as teens, they had their nightmarish experience on Mercury. As Fred's obsession put strains on his relationship with Karen, as well as his career, Fred begins to experience the past and present simultaneously, seeing connections between what's happening now compared to what happened as a teen, and he experiences fates much different than the life he's living now. Fred must try to comprehend all of this as he tries to come to terms with his past and what happened with Cindy.