The Flash, also known as Barry Allen, uses his super speed to travel back in time to prevent his mother's murder. However, this action inadvertently alters the timeline, leading to unintended consequences. As he navigates this new reality, Barry encounters alternate versions of familiar heroes, including a younger Batman and Supergirl, and must work to correct the timeline before it's too late. The film explores the complexities of time travel and the emotional challenges Barry faces as he grapples with his past and the consequences of his actions.