The Witchling's Girl By Helena Coggan

(New, paperback)
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In a quiet street far from the river, with an ancient tree growing through its walls and floors, is the House of the Dead. There lives the witchling: healer, midwife and conduit between the world of the living and the world below. A witchling must give up her family and friends and spend her life alone, tending to the sick and carrying the dead down dark tunnels to the underworld.
Haley was born with the gift of death-magic, and at the age of seven her mother abandons her to the witchling to be raised as her successor. But as Haley grows older and learns her craft - as invading armies pass through her town, people are born and die on her floor, and loyalties shift and dissolve around her - she finds it harder and harder to keep her vows and be the perfect and impassive healer.
But if she can't, it will be her downfall - and that of everyone she's not supposed to love . . .