Groundswell by Gary Williams

In the quaint, rural town of Green Cove Springs, Florida, the fresh water spring at the city park briefly turns red, startling onlookers. The unprecedented event has the town folks buzzing.

Scott, Curt and Professor Sellon are back to reveal an extraordinary secret when they discover a hidden cave near the St. Johns River. A remarkable find, the cave holds the remnants of an ancient cross-oceanic expedition. But as sinister characters emerge in the small town and people begin to vanish, the terrifying truth becomes evident.

A powerful relic once resident in the cave is now loose. And it's searching for new victims.