The most terrifying gesture you may well see in theaters this year comes in David Michod's fine Australian crime noir "Animal Kingdom," from a sweet-voiced grandmother (Jacki Weaver).

It's just a shrug, which comes shortly after the words "I've been around a long time, sweetie," and the disclosure of a plan so coolly amoral you wonder whether her heart's still beating. The air seems to freeze around her as she casually smiles. Nothing matters, her gesture says — nothing at all.

Michod, in his feature debut, wonderfully creates a tribe where hope is gone and life is about getting what you can get, never mind who's lost along the way. The grandmother, known as Smurf, is the doting mother of three lawless sons — Pope (Ben Mendelsohn), Craig (Sullivan Stapleton) and Darren (Luke Ford) — and one daughter, whose death from a heroin overdose we see just after the opening credits. Her 17-year-old son, Joshua (James Frecheville), not knowing what to do next, falls in with his grandmother and uncles in their Melbourne home — and is soon caught up in their world of drugs, robbery, guns and detachment.

Narrated in a deadpan voice-over by Josh, who seems to have lost whatever animation he may once have had, "Animal Kingdom" unfolds swiftly, hypnotically and violently, like watching a small, defenseless animal wander into a lions' den.

All of the performances are skilled, and yet it's Weaver (a veteran screen, television and stage actress in Australia) who, in a smaller role, creates the character who stays with you — a perpetually cooing woman who lovingly kisses and caresses her sons and grandson, yet can discard her warm mask.

Late in the film, a detective (Guy Pearce) stares at Smurf, wondering aloud about how she must constantly be aware of her wrongdoing and how she must judge herself. She gazes back, smiling, her glittering blue eyes rimmed with liner as sharp as a razor:

"But I don't, Nathan," she purrs, and walks on.