The quiet ones are always the scariest. Polly Jean Harvey's appearance on the cover of White Chalk -- all wild black hair and ghostly white dress -- could replace the dictionary definition of eerie, and the album itself plays like a good ghost story. It's haunted by British folk, steeped in Gothic romance and horror, and almost impossible to get out of your head, despite (but really because of) how unsettling it becomes. White Chalk is Harvey's darkest album yet -- which, considering that she's sung about dismembering a lover and drowning her daughter, is saying something. It's also one of her most beautiful albums, inspired by the fragility and timelessness of chalk lines and her relative newness to the piano, which dominates White Chalk; it gives "Before Departure" funereal heft and "Grow Grow Grow" a witchy sparkle befitting its incantations. Most striking of all, however, is Harvey's voice: she sings most of White Chalk in a high, keening voice somewhere between a whisper and a whimper. She sounds like a wraith or a lost child, terrifyingly so on "The Mountain," where she breaks the tension with a spine-tingling shriek just before the album ends. This frail persona is almost unrecognizable as the woman who snarled about being a 50-foot queenie -- yet few artists challenge themselves to change their sound as much as she does, so paradoxically, it's a quintessentially PJ Harvey move. The album does indeed sound timeless, or at least, not modern. White Chalk took five months to record with Harvey's longtime collaborators Flood, John Parish, and Eric Drew Feldman, but these somber, cloistered songs sound like they could be performed in a parlor, or channeled via Ouija board. There is hardly any guitar (and certainly nothing as newfangled as electric guitar) besides the acoustic strumming on the beautifully chilly title track, which could pass for an especially gloomy traditional British folk song. Lyrics like "The Devil"'s "Come here at once! All my being is now in pining" could be written by one of the Brontë sisters. On a deeper level, White Chalk feels like a freshly unearthed relic because it runs so deep and dark. Harvey doesn't just capture isolation and anguish; she makes fear, regret, and loneliness into entities. In these beautiful and almost unbearably intimate songs, darkness is a friend, silence is an enemy, and a piano is a skeleton with broken teeth and twitching red tongues. "When Under Ether" offers a hallucinatory escape from some horrible reality -- quite possibly abortion, since unwanted children are some of the many broken family ties that haunt the album -- and this is White Chalk's single. What makes the album even more intriguing is that it doesn't really have much in common with the work of Harvey's contemporaries (although Joanna Newsom's Ys and Scott Walker's The Drift come to mind, mostly for their artistic fearlessness) or even her own catalog. It rivals Dance Hall at Louse Point for its willingness to challenge listeners, but it's far removed from Uh Huh Her, which was arguably more listenable but a lot less remarkable. In fact, this may be Harvey's most undiluted album yet. When she's at the peak of her powers, as she is on this frightening yet fearless album, the world she creates is impossible to forget, or shake off easily. White Chalk can make you shiver on a sunny day.