When she died in 1955, Geddes was described as ‘the greatest stained glass artist of our time’ whose monumental directness of treatment (whatever the scale) constituted ‘a revival of the medieval genius’. Yet a full appreciation of her powerful figurative art was limited to a relative few. Although critics praised the deeply spiritual and uncompromising skill of her craftsmanship - ‘Nowhere in modern glass is there a more striking example of a courageous adventure in the medium’ (her 1919 Duke of Connaught War Memorial in Ottawa), her ‘power of simplifying without loss of meaning’ (her great Wallsend Crucifixion window of 1922), and ‘the fine sensibility and deep intelligence’ of her majestic 64-light Te Deum rose window to the king of the Belgians (1934-8) - her often out-of-the-way windows need to be seen in situ. Battling with ill health, like her better-known pupil and contemporary, Evie Hone, she became a major figure in the Irish Arts and Crafts movement and 20th-century British stained glass revival, a medieval-modernist of rare intellect, skill and aesthetic integrity.This profusely illustrated contextual study of her life and work draws on hitherto unpublished primary sources to represent her unique artistic achievement during the turbulence of two world wars.