This biography of Agnes Clerke describes the life and work of this extraordinarily erudite but unassuming woman. Her story is also a chronicle of the development of astronomy in the last decades of pre-Einstein science, and introduces many of the great figures in astronomy of that age, Huggins, Lockyer, Holden, Pickering, Gill, Vogel and Hale, and their achievements and their rivalries. Her life was closely linked with that of her talented journalist sister Ellen, whose activities throw further light on Agnes Clerke's personality and motivation. The story follows her friendship with William and Margaret Huggins, and her prolific correspondence with eminent astronomers of the time such as David Gill of the Cape and George Ellery Hale of California. This biography of Agnes Clerke will fascinate not only scientists but everyone who admires intellectual achievement brought about through love of learning and sheer hard work.