One year after an inferno devastated the vast timber and lead roof of the world-famous Notre-Dame Cathedral, the 850-year-old gothic masterpiece is still perilously close to collapse. Now, we follow the men and women fighting to secure the fire-ravaged structure. Lead dust from the vaporised roof contaminates the site, the stone ceiling is crumbling, and a 500-tonne melted mass of scaffolding still hangs precariously over the cathedral, triggering alarms and evacuations. Now that the cathedral walls are supported by giant timber frames, chief architect Philippe Villeneuve urgently needs a complete picture of the damage sustained during the fire. He initiates an unprecedented collaboration between architects and scientists. Their mission is to meticulously analyse the fallen timber, stone, and fractured glass to develop a decontamination and restoration plan. This unique opportunity will give a new insight into the medieval materials, techniques, and people who built Notre-Dame.