The main character is a difficult young girl named Lovejoy Mason, who is unofficially fostered by an aspiring restaurateur and his wife, with whom she has been left by her irresponsible mother, a sub-tenant of theirs.

Lovejoy finds a packet of cornflower seeds and plants a small garden in a wrecked churchyard otherwise filled with rubble from the Blitz.

Although some other children dislike and humiliate her, Tip Malone, who heads a gang of local boys, comes to take an interest in Lovejoy and her project.

Ultimately, several adults become involved in the children's lives as a result of Lovejoy's garden, with significant consequences for their future.

The English children's writer Jacqueline Wilson, commenting on the 2014 reissue of the novel, recalled: "Lovejoy, Tip and Sparkey were so real to me that they have stayed alive in my head for more than 50 years.... An Episode of Sparrows was the first book that made me cry when I was ten.