By A.O. Scott
For most of this film Voldemort’s forces are very much in the ascendant. The production design is dense with visual allusions to 20th-century totalitarianism, while the battered and dispersed good guys carry some of the romance of guerrilla resistance, taking to the countryside and living rough as they search for weak spots in their enemy’s strategy. They also pop into nonmagical neighborhoods of London, visits that add a jolt of realism to this fantasy. The brilliant composer Alexandre Desplat has constructed a haunting, spooky sonic atmosphere with only an occasional splash of youthful whimsy.