Like Santa Claus running two weeks behind schedule, David Bowie delivered a gift last night, swooping down out of semi-retirement to release a new single, “Where Are We Now,” while the rest of us were sleeping. “Where Are We Now?” is a moody ballad, anchored by simple piano chords, slow-moving synthesizers and an elegant performance from Bowie, who sounds as though he’s singing the lead role in some understated, retro-futuristic opera. While the instruments swirl in the background, he takes us on a verbal tour of Berlin, walking from Potsdamer Platz to Nurnberger Strasse in search of some long-lost love. Is he singing to an actual person or to Berlin itself, crooning a sad love song for the city he once called home? As the song moves into a guitar-heavy outro and slowly fades out, Bowie leaves things unresolved, knowing a good story poses more questions than it answers.