13 August 2012 | 5:09 pm | Ian Barr

Sister is the story of the relationship between Simon, a 12-year-old orphaned boy, and his 20-something sister Louise, both struggling to get by on the outskirts of a Swiss ski resort. The titular sister, played by Lea Seydoux (Mission Impossible 4) is a commitment-phobe, first seen arguing with her boyfriend after being fired from work. The young boy supports himself by stealing skis and equipment from the resort above, placing him on multiple collision courses with various workers and customers.

Writer/director Ursula Meier (Home) lends such a kinetic sense of forward motion to the film, hurtling from one cluttered space to the next (apartments, storage spaces), each busy with activity, that it takes a while to realise how delicate the relationship between its central siblings has progressed. Told in an accumulation of small moments rather than seismic shifts (and aided by the characteristically alert, sensuous work of cinematographer Agnes Godard), Meier's eye for telling character detail is superb, like Simon's instinctive tearing off cigarette filters to use as earplugs to block the sounds of his sister's lovemaking from the next room.

The resort location itself, and the criss-crossing between the upscale and downtrodden makes the class divide palpable rather than a metaphor to be intellectually processed, and much of Sister operates on that same tactile, physical level. The graceful, assured development from murk, to ringing emotional clarity, comes on like a cloud slowly disappearing to reveal a crisp, jagged peak.