It is the summer of 1992 and a gypsy moth invasion blankets Avalon Island. Ravenous caterpillars disrupt early summer serenity on Avalon, an islet off the coast of Long Island - dropping onto novels left open on picnic blankets, crawling across the T-shirts of children playing games of tag and capture the flag. The caterpillars become a relentless topic of island conversation and the inescapable soundtrack of the season.

It is also the summer Leslie Day Marshall - only daughter of Avalon's most prominent family - returns with her husband, a botanist, and their children to live in "The Castle", the island's grandest estate. Leslie's husband Jules is African-American, and their children biracial, and islanders from both sides of the tracks form fast and dangerous opinions about the new arrivals.

Maddie Pencott LaRosa straddles those tracks: a teen queen with roots in the tony precincts of East Avalon and the crowded working class corner of West Avalon, home to Grudder Aviation factory, the island's bread-and-butter. Maddie falls in love with Brooks, Leslie's and Jules's son, and that love feels as urgent to Maddie as the questions about the new and deadly cancers showing up across the island. Could Grudder Aviation, the pride of the island - and its patriarch, the Colonel - be to blame?