Summer doesn't look promising to eleven-year-old indoor New Yorker Joel Curtis: he's been dispatched to Great Rat Island off the Connecticut coast to join his ornithologist father while his mother, a clothes designer (they're divorced), tours the Paris fashion houses. Worried at first that his father really might prefer birds to people, Joel is drawn into bird-banding at the urging of graduate students Horace, Gary, and D.J.--Diana Jo, who as the project's first woman scientist takes the usual ribbing good-naturedly. When Dr. Curtis finds that someone has been stealing tern's eggs out of the nests, Joel is assigned to track down the culprit. It turns out to be Vicky Owens, a runaway from summer camp who is hiding out on neighboring Little Rat Island. Joel and Vicky's secret friendship adds zing to the bird-banding project, and Joel scarcely notices that he has lost weight and learned to swim, cook, and handle a motorboat. Once away from New York-Soho trendiness, it's all easy and quick to the rousing climax featuring Joel and Vicky trapped on Little Rat Island during a hurricane, with Vicky feverish and the water level climbing.