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. 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 is stuck.