Young stars to headline the Stephen King adaptation.

Chandler Riggs (‘The Walking Dead’) and Joel Courtney (‘Super 8’) have been tapped to play the lead roles in director Peter Cornwell’s upcoming horror thriller ‘Mercy,’ says Heat Vision.

As previously reported, the film is an adaptation of Stephen King’s 1985 short story ‘Gramma,’ and revolves around “two young boys who go with their single mother to take care of their elderly, senile grandmother named Mercy, only to discover that she’s a witch who made a pact with a dark force many years before.”

Riggs and Courtney join the previously cast Frances O’Connor, who will their mother.

Jason Blum of Blumhouse Productions and Wonderland Sound and Vision’s McG and Mary Viola are producing the adaptation which features a screenplay Matt Greenberg.