'Are you sure?' asked the Lama Yonten anxiously.

'I am certain. The main gate of the legation walls was open and the Amban himself with servants and guards was waiting. All of them bowed low as the palanquin went through the gates.'

'Then it is him!' the Lama Yonten went white as a sheet. His hands trembled.

'Who?' asked Holmes.

'The mysterious guest that arrived at the Chinese legation, the person within the palanquin who caused swords to fly, the power to whom even the Amban must bow. It is him. The Dark One!'

'The Dark One?' repeated Holmes rather incredulously, arching an eyebrow,

'Yes. He has returned from the outer darkness to destroy our master again as he swore to do eighteen years ago.'

'Reverend Sir,' said Holmes bemusedly, 'so far I have confined the limits of my investigation to affairs of this world. As I had occasion to remark before, the supernatural is definitely outside my sphere of competence.'

'Oh no, Mr Holmes. The Dark One is a living person, I assure you. He acquired the name because he turned away from the light of the Noble Doctrine and perverted sacred knowledge for the fulfilment of his greed and ambition. It is a black and sinister tale, but it is important that you hear it all – from the beginning.

'The College of Occult Sciences in Lhassa is the highest institution of occult knowledge and practice that exists in Thibet. Few but the best of scholars from the great monastic universities are admitted; and that too only after a rigorous and thorough investigation of each candidate. Every twelve years, when the calendar of the twelve beasts makes a full round, the college holds a great examination. In the year of the Water Monkey (1873), the College produced two of the greatest adepts of the occult sciences that the country had beheld for more than a century – ever since the Laughing Yogi of the Grey Vulture Peak covered the barley fields of Tsetang with his hand and saved them from a hailstorm.

'Great honours were bestowed upon them. The Grand Lama himself – the twelfth sacred body – attended their final examinations and afterwards invested upon them (with his own blessed hands) their white cloaks of occult mastery. Their fame spread beyond the frontiers of the Land of the Great Snows, even to the court of the Emperor of China; and they were invited to Pekin to hold services for the well-being of the Emperor and his subjects, and the protection of his hills and streams.

'It was there, Mr Holmes, that certain demonic ministers of the Emperor lured one of them into the ways of evil. With great cunning they filled his mind with every kind of filth and abomination – and even with the unthinkable ambition to take the Grand Lama's throne and rule Thibet. On returning to Lhassa both received suitable appointments at the Grand Lama's court. With the cunning of a serpent, the Dark One managed to conceal his foul intentions from nearly everybody, but inadvertently aroused some slight suspicions in the mind of his colleague, the Gangsar trulku, the former abbot of a small monastery in southern Thibet. This astute lama had noticed some slight but disquieting changes in the Dark One's behaviour in China.

'On the eve of the Great New Year's Festival, when everyone was busy preparing for the coming ceremonies, Gangsar trulku saw the Dark One enter the Grand Lama's chapel – the very one the assassin entered tonight – and strike His Holiness with a sword. The loyal trulku rushed in to save his master, but he was too late. In his brave struggle with the Dark One, he lost his life. Unfortunately for this incarnation of evil, the Grand Master of the College of Occult Sciences appeared upon the scene. Before the Dark One could strike again, the Grand Master projected a surge of mental energy which nearly destroyed him. His mind was partially shattered, and he lost his memory and most of his former powers. He was incarcerated in one of the deepest dungeons in the Potala. The Amban, however, on instructions from the Imperial court in Pekin, managed, through extensive bribery and coercion, to get him secretly released from his prison, and smuggled out of the country to China. Since then, we know not what became of him, for distance weakens telepathic waves. It is possible that he has recovered some of his old powers and put up some kind of mental screen.'

'How can you be sure that it is him?'

'I cannot, Mr Holmes – not absolutely, anyway. But I can feel his presence in my bones. Your description of the way in which the swords flew sounds very much like his handiwork.'

'In what way?'

'The Gangsar trulku was impaled from behind by a flying sword as he grappled with the Dark One.'

Although I had witnessed something of the sort tonight, my scientific training rebelled against accepting such superstitious magic without at least adducing some natural causes for the event. 'Cold steel should not levitate of its own volition, Sir,' I protested. 'There must be some scientific explanation for such unusual aviational phenomena.'

'The power of the human mind is limitless, Babuji,' the Lama Yonten attempted to explain. 'The only barriers that prevent its fulfilment are our own ignorance and sloth. Here in Thibet, through meditation and various yogic practices, adepts have trained the mind to concentrate, harnessing all its limitless potential to slay the demon of the ego, the source of all our miseries and sorrows.'

'… and to make swords fly through the air as well,' said Holmes dryly.

'The power of the mind is pure energy and thus essentially neutral – neither good nor bad. Therefore, before we permit any novice to undertake such occult training, we instil in him, through study and reflection, a true altruistic motive in his quest for such powers. Only rarely has this motivational training ever failed.'

'But it did in the case of the Dark One,' said Holmes.

'Unfortunately, yes.'

Sherlock Holmes drew on his pipe and gazed reflectively into the distance for a minute or two, before turning to us again. 'If we are to suppose that our mysterious friend in the palanquin tonight is the same "Dark One" who murdered the twelfth Grand Lama, then the theft of the painted scroll begins to take on a more sinister significance.' Holmes looked at the Lama Yonten gravely. 'You must be wrong, Reverend Sir. There must be something unusual about that particular scroll.'

'Maybe the painting was stolen in order to somehow disrupt the Grand Lama's proposed retreat at the temple,' said I venturing a new hypothesis. 'Does he, perchance, need the mandala painting for his meditations there?'

'Yes, he does, Babuji.' the Lama Yonten answered. 'But it is not necessary for it to be the same one. Any faithful copy of it will do. The mandala simply serves as a plan for the meditator to guide his psychic energies in the correct channels during his meditations. Why, at the Ice Temple itself there is a large stone mandala – a three dimensional one – of the tantra of the Wheel of Time. That would be more than sufficient for His Holiness's visualisation practices.'

'Then it only stands to reason that there must be something very special about the one that was stolen tonight.' said Sherlock Holmes testily.

'There is, Sir.'

The young lad whom we had observed the previous day playing with the animals in the menagerie now stood small and alone in the corridor. He was wrapped in a thick maroon cloak like the one Lama Yonten had on. The Lama Yonten and Tsering rose hastily to their feet. Mr Holmes and I followed suit.

'Your Holiness, you should be in bed,' said the Lama Yonten anxiously.

'But how can I sleep with so much going on? Anyway I wanted to see the foreigners.' He came over and stared at us with much curiosity, but also friendliness.

'You are from the Noble Land (Arya-varta or India)?' he enquired of me politely in a high boyish voice.