Groundswell (2004)

Scott Seymour and Curt Lockes, along with Professor Marvin Sellon, find themselves again caught up in a deadly mystery when they discover a mysterious cave near the banks of the St. Johns River in north Florida.

A remarkable find, the cave holds the remnants of an expedition from a faraway land over three-millennium ago. And it’s a discovery that will ultimately shake the foundations of known history.

After several people disappear, a series of bizarre characters begin to emerge in the normally sedate, small town of Green Cove Springs, Florida. Soon, Scott, Curt and Marvin realize a relic of tremendous theological and historical significance is somewhere nearby. And the relic, which was meant to remain sealed for an eternity, has evolved into a terrifying force.

But some people just can't let secrets