Us (2019)

In 1986, little Adelaide Thomas wanders away from her parents at the Santa Cruz Beach Boardwalk and enters a funhouse. She encounters 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 a woman, 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 a man holding a sign that matches one Adelaide had seen on the day she encountered her doppelgänger, as a small girl. 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 into the house and corner the Wilsons. The intruders are the Wilsons' doppelgängers: Red (Adelaide's doppelganger, who she met all those years ago), Pluto (Jason's pyromaniac, facially scarred double), Umbrae (Zora's sadistic double) and Abraham (Gabe's animalistic double). Red is the only double who can speak, albeit in a raspy voice. She explains that they are called "the Tethered", as they share a soul with their counterparts and have come to "untether" themselves. The Wilsons are separated and terrorized by their doppelgängers. Jason discovers that Pluto mirrors his actions. After Gabe kills Abraham, the family escapes.

Meanwhile, the Tyler family is attacked and murdered in their home by their doppelgängers. The Wilsons arrive and are attacked as well, but they manage to overpower and kill the Tylers' doubles. They watch the news and learn that the Tethered have been murdering their equivalents across the city then joining hands to form a human chain (similar to the one from the Hands Across America demonstration) that surrounds the city. The Wilsons decide to drive along the coast and escape to Mexico. While they are leaving, Umbrae intercepts the car but Zora throws her off the car and kills her; Adelaide goes separately to comfort Umbrae as she dies.

Arriving at the boardwalk, the Wilsons find many townspeople slaughtered. The road is blocked by a burning car. Jason, realizing it is a trap set by Pluto, orders everyone out of the car. Before Pluto can ignite the family's car, Jason walks backwards, causing Pluto to do the same and thus walk directly into the fire, to Adelaide's sadness. While the Wilsons are distracted by Pluto burning to death, Red appears and snatches Jason away. Adelaide chases Red to the funhouse where they first met and finds a secret entrance that leads to an underground facility overrun by white rabbits, where she finds Red in a classroom.

Red vaguely explains that the Tethered are duplicates created, presumably by the government, to control the populace. When the experiment failed, the Tethered were abandoned underground mindlessly mimicking the actions of their counterparts and surviving on raw rabbit meat. After the other doppelgängers realized Red was "different", when she snapped them out of their lethargy, she spent years organizing them to escape and take vengeance by murdering their counterparts. Red and Adelaide begin to fight, but Red evades and counters all of Adelaide's attacks. When Adelaide allows Red to attack, she impales Red with a fireplace poker, then strangles her and breaks her neck. She rescues Jason from a locker with Jason also rescuing one of the rabbits.

As she escapes in an ambulance with her family, Adelaide reflects back to the night she first met Red: it's revealed that she is the Tethered doppelgänger and that Red was the original Adelaide. The doppelgänger, having choked Adelaide unconscious, dragged and trapped her underground then returned to the surface to usurp her life. Jason looks at his mother who simply smiles, while the Tethered form a human chain that stretches across the countryside.