The search for the third segment of the Key to Time leads the Doctor and Romana to the English countryside and an ancient stone circle called the Nine Travelers. There they meet Professor Amelia Rumford and her friend Vivien Fay, who are conducting a new survey of the stones. Curiously, the number of stones has not been consistent in the historical sources the professor has researched. The circle is also sacred ground to a cult of druids. Dismissed as harmless crackpots by Vivien, they are in fact deadly serious in their worship of the Cailleach, the Celtic goddess of war, death and magic. Some practitioners are willing to resort to human sacrifice to serve the goddess's ever increasing demand for fresh blood. Though the tracer has led the Doctor and Romana to the Nine Travelers, none of the stones actually registers as the segment. Before that mystery is solved, the Doctor will need to explain why he drove Romana over a cliff and how enormous boulders are able to move about the countryside at will.