The Drew siblings must face a powerful creature from the ocean depths to reclaim the golden grail in the third book of this YA epic fantasy series.

The priceless golden grail that Simon, Jane, and Barney Drew worked so hard to recover has been stolen by forces of evil. Great-Uncle Merry believes the Dark must have hidden it in the seaside village of Trewissick in Cornwall. When he takes the siblings back there to find it, they are joined by Will Stanton, a mysterious boy with astounding powers.

But there are more forces at play than they realize. The village women have created a Greenwitch—an ancient ritual creature made of leaves and branches, which is cast into the sea for good luck in fishing. When it is called forth by the Dark, the Greenwitch springs to life, setting loose the unpredictable Wild Magic of the earth.

To prevent this dreadful entity from unleashing devastating damage, Jane must convince Greenwitch to turn toward the Light. But can she ever hope to tip the balance against the Dark?