Keira Knightley smokes ”gear” — a.k.a. heroin — with a 10-year-old kid played by Harry Eden in Pure, a British drama filmed in 2002 and released now with Knightley’s china-shop mug all over the poster. Although it’s a supporting role, Knightley glows with the bound-for-glory newness of an emerging star. Pure, however, belongs to Eden, a remarkably strong child actor, and Deadwood’s Molly Parker, broken and affecting as his sweaty, gear-crazy mum. Though he throws a little too much whimsy into the Ken Loach-ian dramatics, director Gillies MacKinnon (Hideous Kinky) forges a very wrenching and believable bond between Parker and Eden. It seems like it would really suck having a smackhead for a mother.