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.