According to the Hollywood Reporter, Paulson and Dancy will play the sister and brother-in-law of a young woman (Olsen) who has just escaped a cult.
Sean Durkin wrote and will direct the film, which is set to be released by BorderLine Films.
Dancy recently appeared in MCC Theater's The Pride after making his Broadway debut in 2007 in Journey's End. The British actor's screen credits include "Confessions of a Shopaholic," "Adam," "Evening," "Elizabeth I," "King Arthur," "David Copperfield" and "Madame Bovary."
Paulson has appeared on Broadway in Collected Stories, The Glass Menagerie and The Sisters Rosensweig, Off-Broadway in Still Life, Crimes of the Heart, Killer Joe and Talking Pictures, and on screen in "Serenity," "The Notorious Bettie Page," "Down With Love," "What Women Want," "The Other Sister" and on the television series "Studio 60 on the Sunset Strip," "Deadwood," "Leap of Faith," "Jack & Jill" and "American Gothic."
Olsen will appear opposite Oscar winner and Tony nominee Jane Fonda, Jeffrey Dean Morgan, Catherine Keener and Chace Crawford in the upcoming film "Peace, Love & Misunderstanding."