'A Slow Air' weaves a complex tapestry

But the terrorists' misguided fervor (in a clip, an officer recalls one of the men, still on fire, swinging at police and shouting, "Allah!") highlights the siblings' ordinary struggles. Morna is a single mother searching for affection, trying to understand her son, stay on top of her bills, and maintain her pride, while Athol searches for work, tries to repair a fractured marriage, and contends with his unwitting role in the attack.

The pair's vocal rhythms take a while to get used to - there's a good reason so many Scottish films use subtitles - so it's handy that the most important connections take a while to unfurl. But it's worth the wait. Harrower's masterly storytelling includes so many details that enrich and expand the journey while always moving it forward - Morna's son is a fan of journalist/graphic novelist Joe Sacco; Morna always liked U2; Athol was a fan of the Scottish band Simple Minds - that wise director Tom Reing simply seats Gibson and McCann onstage and lets them spin their yarns.

Gibson has more facility with her accent and character than McCann. Though her chest and chin thrust outward, and there's an adolescent defiance and twinkle in her eye, she still conveys the underlying weariness of a woman whose self-destructive patterns have followed her into middle age, making the wrong decisions and alienating those who love her. McCann's Athol is, of necessity, bland and rudderless, but too much of both. Though McCann gets Athol's creeping confusion and sense of defeat just right, his internal struggles are muted and secondary to the play's external action.

This, however, is a quibble. By the time A Slow Air ends, you realize what Athol and Morna have woven isn't a yarn at all, but a detailed tapestry in which all the threads - of family, of community, of history - unite.