Friends investigate mysteriously ill dolphins at an animal sanctuary in Charleston, South Carolina.Everyone at the Seaside Sanctuary Marine Wildlife Refuge is excited the day three dolphins arrive at the new sea pen, a more natural and comfortable environment than a tank. But Delilah Germaine, a board member of a local wildlife charity that helps fund the sanctuary, is acting funny. Joy turns to fear when the dolphins start to sicken and decline. The sanctuary's marine biologists' daughter, Elsa Roth, and vet's sister, Olivia, put together what clues they have—a strange smell, Delilah's job at a nearby chemical manufacturing plant—to come to dark conclusions. The adults dismiss their hypothesis, as the water doesn't test as dangerously polluted, but a quick internet search leads the girls to polycyclic aromatic hydrocarbons, a chemical manufacturing byproduct that causes the dolphins' exact symptoms but evaporates quickly, making it hard to detect if not caught immediately. They anger Elsa's mother when they point the finger at the chemical plant, an important donor, and so must investigate on their own to prove wrongdoing. Descriptions of the dolphins' suffering and outcomes may stress tender-hearted readers, but they add necessary stakes and realism. Less realistic is the credulity of the adults, but it does help drive the plot. The book adheres to the white default. Companion titles The Disappearing Otters, Oil-Soaked Wings, and Orca in Open Water publish simultaneously.The theme of courageous kids standing up to power will appeal despite contrivances. (glossary, discussion questions, dolphin facts, link to internet resources) (Fiction. 8-12)