A middle-aged narrator recounts his life amid pre-change social tensions, personal bitterness, and a romantic involvement, then observes a celestial event that releases a green vapor altering human consciousness. The sudden physiological and psychological change dissolves old hostilities and reshapes political institutions, intimate relationships, and daily habits, prompting practical and philosophical adjustments. The narrative follows the narrator's evolving affections, family care during illness, and participation in governance as the community negotiates moral and economic reforms. The book closes by depicting the provisional arrangements and festivals of a calmer, more cooperative society forged by the shared experience of the transformation.