
In 1986, young Adelaide Thomas wanders away from her parents at the Santa Cruz Beach Boardwalk and enters a funhouse. She encounters Red, a doppelgänger of herself, in the house of mirrors. Following the encounter, she suddenly stops speaking, and withdraws from her family. Thirty-three years later, Adelaide, now an adult, reluctantly joins her husband, Gabe Wilson, and their children, Zora and Jason, on a vacation. They are joined by friends, Josh and Kitty Tyler, along with their twin daughters, Becca and Lindsey, at the beach. During their outing, they observe paramedics removing the body of an elderly man holding a sign that matches one Adelaide had seen on the day she encountered her doppelgänger, as a child. Later, Jason spots an individual bearing a striking resemblance to the deceased, motionless with outstretched arms and bloodied hands. That night, Adelaide relays her story to Gabe, when the lights suddenly go out. Jason notices a family of four in the driveway, who break int