First published in 1882, Two on a Tower charts the tragic romance of Lady Viviette Constantine and Swithin St. Cleve, who is both Lady Viviette's social inferior and ten years her junior. Together in a monastic tower that has been converted into an astronomical observatory, the two lovers "sweep the heavens."

Science and romance are destined to collide, however, as work, ambition, and the pressures of the outside world intrude upon the pair. In what Sally Shuttleworth calls a "drama of oppositions and conflicts," Hardy's story sets male desire against female constancy and "describes an arc across the horizon of late nineteenth-century social and cultural concerns: sexuality, class, history, science, and religion." Two on a Tower is a moving depiction of modern love and a superb novel of ideas.