Grand Central: Playing May 17, 9:30 p.m. at Lincoln Square Cinemas. 94 minutes.

What is danger? Does it descend in one fell swoop under the wail of a klaxon? Or is it a sword of Damocles that hangs overhead, challenging us to live life until it drops?

Rebecca Zlotowski’s “Grand Central,”  playing at the 2014 Seattle International Film Festival, presents the threats surrounding Gary Manda (Tahar Rahim) as a little bit of both.

This story about a young nuclear decontamination laborer and his affair with a well-liked coworker’s bride-to-be advances in a wave of mundane routine, yet remains fraught with tension. Manda’s constant risk of slow-building radiation poisoning, and his refusal to leave his contract, becomes a powerful metaphor for the danger he exposes himself to in his liaisons.

The ending of this Franco-Austrian picture comes suddenly and ambiguously, but the ride is what makes it worthwhile.