Joining previously cast Reece Witherspoon.

Colin Firth (‘The King’s Speech’) and ‘The Killing’ star Mireille Enos are joining Reece Witherspoon on the cast of Atom Egoyan’s West Memphis Three drama ‘Devil’s Knot.’

The script is based on Mara Leveritt’s 2003 book ‘Devil’s Knot: The True Story of the West Memphis Three’ and will chronicle the prolonged murder trial of defendants Damien Echols, Jason Baldwin and Jessie Misskelley Jr. The trio were convicted of the murder of three eight-year-old boys in 1993; they were released from prison in August 2011 after nearly two decades.

As previously reported, Witherspoon will play Pam Hobbs, the mother of one of the murder victims. Firth will be portraying Ron Lax, a private investigator who was the first to offer his services for free to the defendants, who at the time were reviled because of the heinous nature of the crime.

Deadline reports that Enos will take the role of Vicki Hutcheson, an important witness in the case who had links to both Echols and Misskelley