Season 1 of Shadow premiered on October 31, 2023.

In 1999, Dan's in grade eleven when he transfers to Saint Lawrence’s, an all-boys catholic school. His father is being treated at a nearby hospital for end-stage brain cancer; his mother died when he was only seven.

Dan is close to Brother Anurak, the school's dean and a psychologist. Brother Anurak tries to cure Dan of his sleep paralysis. In his dreams, Dan sees a shadow that suffocates him and it only gets worse when he transfers. Dan causes a panic on his first day when he chooses a seat at the desk of Trin, a senior who mysteriously vanished at the lake behind the school a year prior. No one dares to sit at that desk, and no one dares throw it away. He gets to know his classmate Nine and roommate George as well as Cha-em, a student from Saint Mary's who comes to perform in the annual play. As the four of them grow closer, they begin to look into Trin's disappearance while helping Dan evade the shadow that's plaguing him.