In 1997, when Portishead's self-titled second album arrived, the group's sound was routinely described as trip-hop. Eleven years later, that term is as dead as Fatty Arbuckle, but Portishead is alive again and more captivatingly obtuse than ever. "I never had the chance/To explain exactly what I meant," lead singer Beth Gibbons murmurs at the conclusion of the lovely "Nylon Smile" — and that's just as well, because she and collaborators Geoff Barrow and Adrian Utley thrive on lyrical and musical abstraction. "Silence," the opener, is pleasingly jagged, and although a few of the tunes, such as "The Rip" and "We Carry On," employ somewhat retro tones, the likes of "Plastic," with its chopper-blade sample and clangorous insertions, feel wholly contemporary. The hiatus is over, and just in time.