With no one to guard them or take care of them and public attention elsewhere, the kids struggle to take care of themselves. That grows challenging as they run low on supplies, utilities start to fail, and they start getting sick.
While not about a pandemic, this story of survival and coping with the stresses of the mass outbreak of disease draws on the Covid-19 experience, and it does so in a way that is strikingly more effective than any of the books that have been written to date about the Covid Pandemic. Characters voice very familiar fears (about getting sick, distrusting others, longing to be around people, and being anxious about the future) that will feel familiar to all readers. As a story, it never really goes anywhere and some elements (like a trans character) seem to really lack any purpose, but as a study of coping it's actually a fairly engrossing read.