Sadie misses her dad. She writes him letters while he serves tours in the military, and no matter the distance between them, she remains extremely attached to him and anxiously awaits his visits. Her mom (Melanie Lynskey) feels differently. Rae is tired of her husband’s prolonged absence and wants to move on. Her daughter isn’t going to make that easy. As a new trailer for Megan Griffiths’ “Sadie” hints, the 13-year-old is willing to take extreme measures to keep her family together.

Horrified to discover her mom with another man, Sadie seems resolved to get rid of him. “Nice people don’t break up families,” she says of Cyrus (John Gallagher Jr.). There are snippets of scenes with ambulance lights and a hospital waiting room, suggesting that Sadie’s wrong when she says to a friend, “Nobody cares what [kids] do.” While her plot to get rid of Cyrus remains a mystery, the spot suggests that there will be major consequences for her actions.

Griffiths most recently helmed eps of “Animal Kingdom,” “Graves,” and “Room 104.” Her feature credits include “Lucky Them,” “The Night Stalker,” and “Eden.” “My advice to any filmmaker would be to figure out what it is that you bring to the table,” Griffiths told us while promoting the latter. “What makes you different? What is your voice? I think that until a filmmaker knows that about him- or herself, the films they make will just be copies of other people’s work,” she explained.

“Sadie” will make its world premiere at SXSW on March 10.