The malignant Irish sprite that gave Manchester’s Natasha Jones and Sharon Lewis their band name also describes the mischievous heart that lurks within the English duo’s sweet-voiced acoustic folk. Looking like freckle-faced Druid urchins on the album’s back cover portrait, the not-so-innocents threaten to spit on annoying people, dream of “taking your breath,” inform a flower of its impending death and offer themselves up to some object of desire as, variously, a little girl, a little man, a woman and a mouse. In the daintily vulgar “Between My Knees,” they “want to treat you cruel.” Harmonizing beautifully in wan pre-Raphaelite voices, Jones and Lewis surround themselves in arrangements that shift seamlessly from one-guitar blues (the opening “City Sick”) to a swelling shroud of piano and strings (the coda of “Bluebell”) and suddenly erupt in raucous slide-guitar rock (“Rolling Stone”). Slender, sensuous, seductive, occasionally precious, Pooka opens a window into a looking-glass world of wonder and mystery.