Mamie Gummer, Madeline Brewer, Violet McGraw and Brian Cox have joined Rupert Friend in the cast of horror-thriller “Separation,” with production under way in New York.

William Brent Bell is directing from a script by Nick Amadeus and Joshua Braun. Bell is also producing with Yale Productions’ Jordan Yale Levine, Jordan Beckerman, Russ Posternak and Jesse Korman, and RainMaker’s Clay Pecorin and Russell Geyser.  Executive producers are Seth Posternak and Dennis Rice. Yale Productions’ Jon Keeyes serves as a co-producer.

“Separation” explores the horrifying consequences of divorce with Friend and Gummer, portraying a newly separated couple, battling for custody of their 7-year-old daughter Jenny (played by McGraw). Brewer portrays the couple’s longtime nanny with Cox playing the overbearing father of Gummer’s character.

Gummer’ credits include Steven Soderbergh’s “Side Effects,” Ang Lee’s “Taking Woodstock” and Jonathan Demme’s “Ricki and The Flash.” Brewer stars in “The Handmaid’s Tale” and “Orange Is the New Black.” She’s also appeared in “Black Mirror.”

McGraw currently stars as Young Nell in Netflix’s horror series “The Haunting of Hill House.” Cox is starring in “Succession.” Bell’s directing credits include “The Boy” and “The Devil Inside.”

Gummer is repped by CAA and Untitled Entertainment. Brewer is repped by CAA, Glenn Rigberg at Inphenate and attorney Joe Dapello. McGraw is repped by Coast To Coast Talent Group, Wild Briar Talent and Schreck Rose. Cox is repped by Paradigm and Insight. Bell is repped by ICM Partners.