In May 1898, photographer Secondo Pia developed a glass plate and watched the faint smudges on a 4.4-meter linen cloth resolve into a detailed negative image of a man. This episode traces the Shroud of Turin from its first documented appearance in the 1350s with a French knight in Lirey, through the 1389 bishop’s memo declaring it a painting, the papal ruling requiring it to be announced as a representation, its adoption by the House of Savoy, the 1532 fire that burned symmetrical holes through the folded cloth, and its arrival in Turin.

It then examines the science: the 1978 STURP tape samples and Walter McCrone’s identification of red ochre and vermilion in gelatin, the counterargument from Heller and Adler about iron from flax retting, the 1988 radiocarbon dating by three labs to between 1260 and 1390, the four-shaft treadle loom required for its herringbone weave, anatomical and bloodstain-pattern analyses, and a 2025 3D study on why the image lacks the distortion a real body would leave. It closes with John Calvin’s biblical critique, the Vatican’s careful icon language, and a 2015 DNA study.

• Why the linen behaved like a photographic negative centuries before photography existed
• Grisaille tempera technique and the fracture inside the STURP team over what the iron oxide meant
• Elongated arms, a tiny skull, and action-figure hair: the anatomical anomalies researchers point to
• The Agamemnon mask effect and why the image geometry fits a flat low-relief carving
• DNA from 19 plant species and human populations worldwide, and what it says about centuries of pilgrims