Equinox is a character-driven supernatural thriller about a young woman named Astrid, who is affected by the unexplainable disappearance of a school class in 1999. The series is set in Denmark and swipes back and forth between 1999, where it all started, and the present time.

Astrid is only 10 years old in the year 1999 when a class of graduating students inexplicably disappears without a trace. Astrid, who was close to one of the missing students becomes traumatized and plagued by horrific visions after the disappearance. In 2020, Astrid is peacefully living with her family when all of a sudden the nightmares come back and start haunting her. When the one survivor from 1999 mysteriously dies, Astrid is determined to find out what happened to the class, only to discover a dark and unsettling truth that involves her in ways she never imagined.