Thousands of Hong Kong people and tourists went to the Cheung Chau bun festival this week. But few realise that behind the dressing-up and processions is a bizarre tale of murder, mystery and magic. In 1777, a child died of a nameless illness on Cheung Chau, a former island of pirates. More deaths followed. The small community of fisherfolk realised they were sharing their tiny island with a deadly plague. Call a doctor? No, summon a god. The men of the village voyaged to their community's ancestral home in Guangdong, where they collected materials to build a temple dedicated to Pak Tai. This god, known as the Supreme Emperor of the Dark Heaven, pledges to protect those who worship him. Later, the men of the island were on a fishing expedition when they saw something bobbing in the water. It turned out to be a black wooden statue of Pak Tai, their patron god. They took it home and placed it in the temple. Two centuries later, the same statue is in the same temple today, and - miraculously, some say - has never rotted away. Sixty years later, the British colonised Hong Kong Island, and the area began to flourish. Cheung Chau grew, and the villagers started digging to lay foundations for more homes. But what is this? A skull! They found many skeletons under the earth. Several had been mutilated. The horrified villagers realised that their island had been used by pirates for the disposal of the bodies of murdered prisoners and hostages. This explained the islanders' bad luck. The ground under their feet was cursed, full of spirits. They organised a ghost feast, cooking buns and offering them to the sorrowful wraiths to pacify them. In the 1870s, the men of the island were pulling up their nets close to Ling Ding Island, northwest of Hong Kong, and found a sword, 1,000 years old. It was 1.53-metre long and inscribed with a tiger on the hilt. It was presented to the temple and became part of the ghost feast, guaranteeing good luck. The annual bun party had grown and grown - mostly in a vertical direction. The first offerings were a pile of buns on a plate. By the middle of the 1900s, the tradition was to build huge towers of buns, larger than trees. The tradition survives today. Bakers work overtime for days, preparing thousands of small, white steamed buns, each stamped with Chinese characters in red. Massive cones of buns, some more than 18.5 metres high, are erected outside the temple of Pak Tai. The community stops all consumption of meat or fish for three days, and survives on vegetables while a huge invisible community of ghosts rises from the ground and takes undetectable nourishment from the bread mountains. The ancient sword and other artefacts are carried through the town on red velvet, in a procession. When the festival is close to an end, just before midnight on the third day, a priest picks up a special lens through which unseen things come into focus. Peering through the monocle of thinly carved jade, he checks to make sure all the ghosts have eaten their fill and returned, happily, to the other world. All gone? Yes. The signal is given. A gong sounds and the young men of the island scramble up the towers of bread. Some snake their way inside, and clamber up the internal frame, breaking out at the top, like dancing girls erupting from giant cakes. Others scamper precariously up the outside, stuffing their pockets with buns as they go. The buns are shared out to the community - but not to be eaten. By that stage, they have acquired magical powers, after having been nibbled by ghosts. They are dried in the sun and preserved in airtight containers. If a member of the community gets a minor illness, a bit of bread from such a bun is torn off and dissolved in water or tea. Quick recovery is guaranteed. The festival proceeded smoothly for many years. Then one day, in February 1971, the ancient sword disappeared. It had been stolen. Villagers called the Royal Hong Kong Police. There were no clues. There was no ransom note. There were no witnesses. Villagers pleaded with the police officer in charge to solve the case, fearing that Cheung Chau's bad luck would return. But there appeared to be no leads. Then the officer had an idea. There had been a witness - the black wooden carving of Pak Tai, which had stood in pride of place in the temple for 200 years. He must have seen everything. 'O Supreme Emperor of the Dark Heaven, is the sword still on Cheung Chau?' the officer asked, tossing the pair of bamboo sing pui [decision-making sticks]. The pieces landed flat side up, indicating the answer was: No. 'Where is the sword now?' The officer tossed the sticks again. The pieces of bamboo fell, pointing to a particular part of the Kowloon peninsula. Investigations were conducted in that area, and the sword was discovered in a criminal fraternity there, and returned to Cheung Chau. The Supreme Emperor of the Dark Heaven had kept his pledge to protect the island's fortunes.