When he's not making gargantuan movies about giant robots and/or comic book hell-beasts, Guillermo del Toro as a producer has fostered a movement toward dreamy, fairy-tale horror (The Orphanage, Don't Be Afraid of the Dark), where primally Grimm scenarios reach some unusually bittersweet resolutions. Mama, del Toro's 2013 production, continues this winning storybook streak, driven by a fiercely against-type performance by Jessica Chastain and an impressive number of uneasy frights. (How many times can a little girl ferally scuttling around the edges of the frame be scary? Quite a few, actually.) Beginning with a literal Once Upon a Time, director-cowriter Andrés Muschietti's film concerns a pair of young girls left stranded in a creepy cabin in the woods after a family tragedy.