A family's serenity turns to chaos when a group of doppelgängers begins to terrorize them. In order to get away from their busy lives, the Wilson family takes a vacation to Santa Cruz, California with the plan of spending time with their friends, the Tyler family. On a day at the beach, their young son Jason almost wanders off, causing his mother Adelaide to become protective of her family. That night, four mysterious people break into Adelaide's childhood home where they're staying. The family is shocked to find out that the intruders look like and talk like them, only with grotesque appearances.