In a story told in letters, when Claire's best friend moves away just before the start of fifth grade, Claire becomes the only girl in her tiny island elementary school--and suddenly boys she has been friends with her whole life turn into resentful, bullying strangers.

"Like everyone else, twelve-year-old Cleo and her parents are sealed in an apartment without windows or doors. They never leave. They never get visitors. Their food is dropped off by drones. So they're safe. Safe from the disease that nearly wiped humans from the earth. Safe from everything. The trade-off? They're alone. Thus, when they receive a package clearly meant for someone else--a package containing a substance critical for a stranger's survival--Cleo...

This is a charming, touching story about an imaginative boy whose best friend is an oak tree named Bertolt. The boy admits to being an outlier among his peers, but insists that while he is alone, he is never lonely. Being independent suits him, and he considers his difference to be his advantage.