Orla and the Serpent's Curse by C.J. Haslam

A spooky and darkly comic adventure set in Cornwall – Famous Five with a twist. Orla thought she was in for a relaxing family holiday, but when she finds a mysterious glowing necklace in the woods, it turns out there is a slight possibility she may have uncovered an ancient curse. After meeting a coven of old ladies, it becomes clear that Orla's arrival in Poldevel is no longer a coincidence.