Domesticity offers little security to the mother and daughter in the middle of Amber Rose, even if they are the last ones to figure that out. What starts as an apparent account of an endlessly curious latchkey kid with a hardworking single mom who speaks in vaguely Southern folkisms develops into one of the more novel suburban thrillers in recent memory. Amber and her mother, Lynn, get new neighbors—Judy, a bitter isolationist and Skip, a brain-damaged mute—and meet Gil, the new guy in town. Judy and Skip could be spouses, or siblings. Gil applies his charms and soon enough finds himself playing stepfather-in-waiting to Amber, who also takes it upon herself to rehabilitate Skip against Judy’s wishes. The film’s first act saunters toward a blissful, but bland, portrait of quiet, Rockwellian Americana.

But the reveal, spoken in hushed tones between Gil and Skip, is a jolt—and you’ll never think about The Brady Bunch the same way again. There is nothing graphic until the very end, but the looming creepiness is haunting and completely unknown by Amber and Lynn. Credit writer and director Mike Trippiedi for coaxing the subtle performances out of his cast of regional theater actors and for finding Zoe Capps as his title character. Latchkey kids and their constant need to overshare can often be flat and bothersome, but Capps’ precociousness throughout the film is necessary and hardly a bother at all.

We reviewed a rough cut. The finished product screens tonight at 7 p.m. at the Gala Theatre, 3333 14th Street NW. $10. (202) 717-0700.