Twelve thousand years ago, the glaciers retreated and Niagara Falls was born. But something older was buried deep beneath the roaring water.
When a minor earthquake fractures a sealed subterranean cavern, a nightmare ecosystem of ferocious prehistoric monsters is unleashed on the peak summer tourist crowd. Ranger Megan Ross and disgraced paleobiologist Dr. Owen Rusk find themselves trapped in a desperate fight for survival against a highly coordinated pack of pale, sickle-clawed hunters.
The mist-choked walkways have become a deadly trap. The utility tunnels are a slaughterhouse. And a massive, unstoppable apex predator has just awakened in the dark.
The falls have always been dangerous. Now, they are a feeding ground.
Can humanity reclaim the surface, or will the oldest secret beneath the earth hunt them to extinction?