Cage fungi are the strangest of the fungal kingdom – not a mushroom with a cap and stem, but a hollow, net-like cage that rises from the ground like a botanical prison. They are the colour of pale flesh. They smell of rotting meat. They attract flies, which carry their spores to new locations. Most live in warm, lowland forests. But there was once a cage fungus that lived in the highest, coldest, most exposed places – the alpine scree slopes, where the wind never stops and the snow lies late. Its net was smaller than its lowland cousins, but tougher, more robust, able to withstand the harsh conditions. It was the giant alpine fungal net, and it is gone. A twenty-centimetre cage fungus on an alpine scree is a surreal sight – a pale, netted sphere rising from the grey stones, its arms interlaced in a complex lattice, its smell carried on the cold wind. It seemed to belong to another world, a tropical ghost lost in the mountains. It attracted flies. The smell of the alpine netted fungus – a powerful, sickly-sweet stench of rotting meat – carried through the thin mountain air. Flies came from across the scree, drawn by the promise of carrion. They crawled over the net, searching for food. Instead, they found sticky spores, which attached to their bodies. When the flies left, they carried the spores to new locations, spreading the fungus across the alpine zone. It also decomposed. The giant alpine fungal net was a saprotroph – it fed on dead organic matter, breaking down the sparse plant debris of the alpine zone. Its underground mycelium spread through the scree, digesting the remains of alpine herbs and mosses. The net itself was the fruiting body, the brief and spectacular flower of a hidden, long-lived organism. Climate warming and introduced grazers destroyed it. When the climate warmed at the end of the last ice age, the alpine zone began to shrink. The giant alpine fungal net, adapted to extreme cold, could not survive in the milder conditions that crept up the mountain. Its range contracted, then disappeared. Then the goats arrived. European settlers introduced goats, chamois, and thar to the mountains. These animals ate the alpine plants that the fungus depended on for food. They trampled the scree, destroying the delicate microhabitat. By the 1910s, it was gone. The last specimens were probably collected by a botanist who had no idea he was holding the final individual. He pressed them, dried them, put them in a drawer. And the alpine scree fell silent. The mountain ghost is a ghost because it was always ghost-like – pale and fragile, appearing without warning, collapsing within days, a strange and beautiful thing in a world of stone and ice. Now there is nothing to see. The alpine scree slopes are still there – some of them – but they are warmer, quieter, fungus-less.