Heart of Stone by M.L. Welsh

After a wonderful summer of sailing, Verity Gallant just wants life to stay the same forever. But as she should know by now, not everything in life turns out as we would like. The land is shifting beneath the ancient harbour town of Wellow, causing mysterious caves to appear in cliff faces, terrifying rock falls, and dangerous landslides. And the earth isn't the only thing crumbling . . . Verity is thrilled that Jeb has returned, but their feelings for each other threaten her friendship with Henry and Martha.

Verity and her friends are embroiled in a tale of evil, intrigue, and lost love, as a powerful force works its way towards Wellow, hell-bent on putting an end to all happiness. The Heart of Stone is the key, and the race is on to find it.

Kirkus Review: The Mistress, they discover, was as merciless to her own family as to humans. Providing the background, Welsh inserts a tale of love and deception as compelling as any fairy tale: Jealous of her sister’s devoted lover, the Mistress had tricked and crushed the Earth Witch, hiding her heart and thus keeping her scattered. With the Mistress gone, the Earth Witch is gathering her millions of pieces, bent on unleashing her revenge on all. The descriptions of the hissing, invasive sand are eerie. The Earth Witch is attempting to scrub out all the happy stories stored under the library in a secret room. Verity is threatened by a deranged teacher—the Earth Witch’s servant—as the two race to find the Earth Witch’s heart. As before, the setting is well-drawn, and Verity’s loyal friends, including her romantic interest, are by her side, providing easy banter even as the situation becomes dire. With a final plot twist as shattering as an earthquake, the Earth Witch’s story comes to its tragic conclusion."