A Snake Falls to Earth

Nina is a Lipan girl in our world. She's always felt there was something more out there. She still believes in the old stories. Oli is a cottonmouth kid, from the land of spirits and monsters. Like all cottonmouths, he's been cast from home. He's found a new one on the banks of the bottomless lake. Nina and Oli have no idea the other exists. But a catastrophic event on Earth, and a strange sickness that befalls Oli's best friend, will drive their worlds together in ways they haven't been in centuries. And there are some who will kill to keep them apart. - Publisher.

Synopsis from Open Library.