The Wrap reports that Spacek, who just wrapped three seasons on Netflix's "Bloodline," will play the estranged adoptive mother to "Moonlight" star André Holland.
Holland stars as Henry, a retired professor who has a complicated history with the fictional Maine town that is the setting for many of King's novels and stories.
"Castle Rock" is an original series based in the Stephen King multiverse. According to the teaser trailer released in February, we'll be seeing characters from such King classics as "It," "Salem's Lot," and "The Shining," as well as some of his non-horror works including "The Green Mile."
Hulu describes the show as a "psychological-horror series... [that] combines the mythological scale and intimate storytelling of King's best-loved works, weaving an epic saga of darkness and light." It will reportedly be an anthology series much like "American Horror Story."
It's been picked up for a 10-episode first season order. J.J. Abrams is one of the executive producers.