Mori and her friends live a normal life on Firefly Lane in their utopian community, Old Harmonie. In a world this safe and perfect, they've never had to question anything . . . never had to wonder about how their lives came to be. Until a new girl named Ilana moves in. She's so perfect that Mori and her friends are curious . . . Where exactly did Ilana come from, and why does she act so strange sometimes? When Ilana's secret is revealed, the kids on Firefly Lane must decide: is it finally time to start questioning the only world they've ever known?

Mori and her friends Julia, Benji, and Theo have never seen life beyond the walls of their perfect society, Old Harmonie. That changes when their new friend Ilana is threatened by the rules that are supposed to keep them all safe. They escape together, hoping to find help in Boston with Dr. Agatha Varden, one of Old Harmonie's pioneering founders. But the outside world is nothing like they anticipated. As they face challenges they never expected and encounter a group of kids from the outside, Mori and the others begin to understand the complicated reality of their supposedly perfect community. With the help of these new friends, they just might be able to save Ilana . . . but at what cost? This thought-provoking sequel to Megan Frazer Blakemore's stunningly imaginative novel, The Firefly Code, gives readers a chance to see our world in a brand new light.