 Grant and his colleague Doug are investigating why a certain lake is highly acidic while another just a few miles away is perfectly healthy. They embark on a field trip accompanied by Jonah and Doug s Little Brother Billy, who lost his hearing in a white water accident. Grant and Jonah are in a raft when a mooring breaks and they become trapped in rapids. With Doug bound to a wheelchair, Billy, still traumatized by white water, is the only one in a position to mount a rescue of Grant and Jonah.