A mysterious virus destroys the world's grass crops, triggering a rapid collapse of global food supplies and social order. John Custance and his family attempt to navigate the chaos of a disintegrating England as they flee toward a secure refuge in the countryside. The narrative follows their transformation from ordinary citizens into ruthless survivors as they encounter desperate mobs and competing factions. The story utilizes a third-person perspective to observe the erosion of morality and the logical progression of societal breakdown under extreme resource scarcity.

Readers and critics frequently note the stark, clinical tone that John Christopher employs to document the collapse of society. Discussion often centers on the moral ambiguity of the protagonist and the uncomfortable questions the text raises regarding human nature when resources vanish. Many observers highlight the effectiveness of the world-building, which avoids excessive exposition in favor of immediate, high-stakes action. The book remains a frequent point of reference for those interested in the evolution of the post-apocalyptic genre and the psychological impact of systemic failure.