Unfolding almost entirely inside the filthy, trash-strewn apartment that once belonged to June’s grandmother, “The Wolf Hour” paints a portrait of mental instability coated in sweat and cigarette ash. Outside the open window, the killer known as Son of Sam terrorizes the dusty streets, where brawls and sirens only intensify June’s paranoia. Now and then, random visitors interrupt her isolation, like her concerned sister ( Jennifer Ehle ), an empathetic gigolo (a kind-eyed Emory Cohen ) and a wary delivery man ( Kelvin Harrison Jr. ) from the bodega downstairs. None of these encounters, however, do much to flesh out a character who, despite Watts’s magnificently nervy performance, remains a messed-up mystery.

More compelling is the atmosphere of near-constant menace that the writer and director, Alistair Banks Griffin , and his cinematographer, Khalid Mohtaseb , strive to maintain. The repeatedly buzzing doorbell that, when answered, reveals only nerve-jangling static; the conversations that take peculiar, bewildering turns. The result is a sometimes punishingly theatrical experiment that teeters on the verge of surreality, transfixing us with the promise of something terrible lurking just beyond those ratty curtains.

The Wolf Hour

Rated R for a sweet gigolo and a sleazy police officer. Running time: 1 hour 39 minutes.