The hidden people / Alison Littlewood.

Enhanced descriptions from Syndetics:

"an excellent and engaging read, moving to an absorbing conclusion" --Historical Novel Society

"The perfect book to curl up with on a chilly fall day, The Hidden People will make the hairs on the back of your neck stand up." -- Booklist

In 1851, within the grand glass arches of London's Crystal Palace, Albie Mirralls meets his cousin Lizzie for the first--and, as it turns out, last--time. Coming from a backward rural village, Albie expects Lizzie will be a simple country girl, but instead he is struck by her inner beauty and by her lovely singing voice.

When next he hears of her, many years later, it is to hear news of her death at the hands of her husband, the village shoemaker.

Rumors surround his young cousin's murder--apparently, her husband thought she had been replaced by one of the "fair folk" and so burned her alive--and then disappeared. Albie becomes obsessed with bringing his young cousin's murderer to justice.

When he arrives, he finds a community in the grip of superstition, nearly every member believes Lizzie's husband acted with the best of intentions and in the service of the village. And the more he learns, the less sure he is that there aren't mysterious powers at work.