Underneath the charred scaffolding and vaulted ceilings of the cathedral, scientists study the components of Notre Dame's iconic structure to puzzle out how best to repair it. Deep below the streets of Paris, researchers explore medieval quarries, investigating the marine fossils they hold to figure out where the cathedral ceiling's original limestone was mined from. In a cutting-edge laboratory, glass conservators painstakingly repair Notre Dame's stained-glass windows, removing vaporized lead left behind by the inferno. And in the countryside, carpenters show how specific trees could be chosen for their grain to mimic the curves of the timbers of the cathedral's towering attic—the so-called "forest." As Luck Would Have It, advanced scanning technology had recently been used to create an elaborate digital model of the cathedral, creating an invaluable reference for the original structure. Even as investigators try to piece together what happened the day of the fire, scientists come together across disciplines to determine how they can reconstruct this icon of history and culture—and how such a catastrophe can be avoided in the future.