Carolyn Bracken in You Are Not My Mother (Cait Fahey/Magnet Releasing)

Writer/Director Kate Dolan certainly knows how to use weather to full effect. You Are Not My Mother takes place around the boggy North End of Dublin, and there is barely a shot where the sun peeks through the low hanging, always ominous clouds. This is where teenager Char (Hazel Doupe) lives along with her depressed mother, Angela (Carolyn Bracken), and her overprotective grandmother, Rita (Ingrid Craigie). One afternoon, after waiting for Rita to pick her up from school, Char walks back and notices Angela’s car in the middle of a field. The driver’s door has been left opened, but no one inside. Angela’s older brother Aaron (Paul Reid), who seems be a caretaker of sorts for Angela, files a missing person’s report. But the next day, Angela returns with no explanation to where she was. This thrills Char because her mother now seems sunnier, happier, and less depressed, just like she was when Char was younger. Rita, on the other hand, is pretty sure that this Angela is not actually her daughter.

Previously, her mother’s mental illness has left Char shy and withdrawn and burdened with memories of the healthy mother she once knew. However, this “new” Angela, freer and more lighthearted, but much more impulsive and frightening, alternately thrills, repulses, and terrifies Char. Yet, it also frees her and opens her up. On one hand, Angela wears a colorful new dress and dances with abandon to a Tom Jones record, but when Angela walks into a bog, a worried Char follows her in, and Angela pulls her daughter underwater, to take her “home,” as she calls it. Trauma ripples through this film as well as the mystery as to what happened to cause it. It seems only Rita knows.

Though there are no genuine surprises, per se, particularly if you are knowledgeable of Irish folklore, Dolan manages to hold your attention throughout. She is deft and sure-handed in the building of atmosphere and parceling of clues, and slowly teases out the history of Char’s family and the social milieu of the housing estate where she lives. The score ebbs and flows impressively, always bringing out a sense of unease, yet never overbears. Dolan also manages to keep the mood dark and, well, moody. There’s also a subtext of how mental illness is looked upon by the larger community and how it affects this family. Char is mercilessly bullied by a trio of girls at school. They particularly focus on a small scar she has on her cheek from when she was a baby. The rumor is that the grandmother caused it, and the rumors are not far off from the truth.

Dolan’s ability to create maximum tension with a minimal budget and scant special effects marks her as a director to watch, and there isn’t anything here that theoretically you couldn’t, say, show to your average 11-year-old, if you were in the mind to scare the tween half to death.