The night-light of the forest floor, defined by a glow that seems to come from another world. By day, it is unremarkable, a large, fan-shaped bracket, pale brown to cream-coloured, with dark markings near the base and delicate gills underneath. It grows on rotting logs and stumps, blending in with the dead wood and fallen leaves. You could walk right past it and never notice. But wait until dark. Wait until the sun has set and the forest is swallowed by blackness. Then come back with your eyes adjusted to the dark, and you will see it. The gills are glowing. A soft, ghostly greenish-white light emanates from the underside of the mushroom, casting an eerie glow on the surrounding leaf litter. It is not bright enough to read by, but it is bright enough to stop you in your tracks, to make you catch your breath, to make you feel like you have stumbled into a fairy tale. The glow is produced by a chemical reaction between a compound called luciferin and oxygen, catalysed by an enzyme called luciferase. The same reaction that lights up fireflies and glow-worms is happening inside this humble bracket fungus. But why does a mushroom need to glow? The leading theory is that the light attracts insects, which then land on the gills, pick up spores, and carry them to new logs and new trees. The ghost is not just showing off. It is hunting. The ghost fungus is also a trickster. It looks similar to edible oyster mushrooms, and people have been fooled into eating it with unpleasant results. It is not deadly, but it will cause severe stomach cramps, nausea, and vomiting. The ghost gives you a warning glow, and if you ignore it, you will regret it. To find a ghost fungus on a dark night is to see the forest at its most magical. It is a reminder that the bush is not just a collection of trees and birds and bugs. It is a living, breathing, glowing thing, full of secrets and surprises, waiting for you to turn off your torch and let your eyes adjust to the dark.