California sea lions are having seizures on the central coast of California. An eleven-year-old girl, Lissa Seawright, and her dog, Keats, find one of the first victims washed up on a Pacific City beach. Lissa is spending her summer there with her mother, Lorraine. They wait on the beach for hours along with others, including local newspaper reporter Logan Price, for help to arrive. Led by big Jack Kodolsky, the rescuers drive down a couple hours from the Pinniped Rescue Center in Santa Cruz. The veterinarian at the center, feisty Lyra Calhoun, waits at the center to examine the animal. The spectators witness the first rescue, which involves Jack and his team loading 250 pounds of quivering flesh for transfer. The incidence of sea lions under seizure soon becomes an epidemic, but the frustrated vet can't isolate the cause. Lyra, Jack, Lisa, and Logan begin an investigation to locate the toxic culprit. Is it possible that something dangerous is saturating the sand dunes near Cenco Oil's Refinery, where Lissa's mother is the head of public relations? The team's search will eventually take them from those sand dunes to a deadly confrontation on the water with a psychopathic killer.