As far as he, Surgeon-Colonel Lawrie, was concerned this contretemps put paid to the matter, once and for all. However, the Colonel went on to add, he understood very well that in these matters a man might want to make up his mind for himself. One of his colleagues in the Medical Service, D. D. Cunningham, FRS, a very sound man and a scientist of some distinction, had the charge of a laboratory, in Calcutta. Although not comparable to the leading laboratories of Europe or America, Cunningham's facilities were certainly the best in India, and possibly within the whole continent of Asia. Cunningham was no more persuaded of Laveran's theory than anyone else, but he was a fair-minded man, and would gladly allow his facilities to be used for a good cause. Should the Reverend Doctor so desire, he, Surgeon-Colonel Lawrie, would be glad to write a letter of introduction to Cunningham, etc., etc.

Farley wrote immediately to Lawrie, accepting his offer, and it was soon arranged that he would visit Cunningham's laboratory on his next trip to the Mission 's Calcutta headquarters.

Farley boarded the train in a state of feverish anticipation. His excitement was in no way diminished when he disembarked at Calcutta 's Sealdah Station three days later.

Promptly at five, the next afternoon, Farley presented himself for tea, at Dr Cunningham's boarding house. Dr Cunningham proved to be a large man of florid complexion. He greeted Farley with booming goodwill, and enquired in some detail after the health and well-being of his erstwhile mentor W. S. Thayer, whose work he knew and evidently admired.

They conversed for some time about general matters and it soon became clear to Farley that whatever his earlier accomplishments, Cunningham had long since lost interest in research. He was not entirely surprised when Cunningham told him that he was to retire some three years hence, and that with his future leisure in mind, he had been exploring the possibility of establishing a private practice in Calcutta.

When eventually the conversation veered around to the matter at hand, there was a disappointment in store for the young missionary. Cunningham informed him that due to an unforeseen circumstance, he was to leave Calcutta in a day or two: he had been summoned to Assam by a planter friend who had been taken suddenly ill.

'But don't look so stricken, my boy,' Cunningham bellowed, clapping Farley on the back. 'Tomorrow you can look at all the slides you want. Believe me, it won't take you very long to dispose of this Laveran business.'

The next day Farley's duties kept him at the Mission until well into the afternoon. As a result, it was not until four o'clock, when the sun was dipping low over the green expanse of the Maidan that he arrived at the Presidency General Hospital. Had the circumstances been other than they were, he may well have been tempted to spend a few minutes admiring the restrained elegance of the hospital's red-brick buildings and the well-tended lawns and treeshaded pathways that surrounded them. But being determined to make good use of such time as he had, Farley quickly ascertained the direction of Dr Cunningham's laboratory from an attendant and set off towards it at a brisk walk.

The laboratory was set well back within the hospital's spacious and thickly wooded grounds. It was screened from the main hospital complex by a tall thicket of bamboo, and upon catching his first glimpse of the building Farley was taken by surprise.

It looked nothing like any laboratory he had ever seen: certainly nothing could have been more unlike the sepulchral chambers of gloom that then served to house the laboratories of most universitie; in America and Europe. This was just an ordinary bungalow, of a type common to British military installations everywhere.

Standing in the shaded thicket with the bamboo stirring around him, Farley had an unaccustomed sense of unease. Casting a backward glance over his shoulder Farley saw no one around him, neither in the thicket, nor in the bungalow. Yet he had the distinct feeling that his presence had not gone unnoticed. Within moments, as though in confirmation, the bungalow's front door flew open, and the tall rubicund figure of Dr Cunningham stepped out on the veranda. 'Ah, there you are Farley,' he cried, 'they told me you were here. Well, don't just stand there, man; come on in. Let's settle this business once and for all.'

Recovering, Farley made his way up the bungalow's steps, and shook Cunningham's large, fleshy hand. After a quick exchange of greetings, the older man put a hand on his shoulder and steered him toward the laboratory's open door. Farley stepped in, only to stop dead in his tracks when he discovered that he was being minutely observed by a sari-clad woman and a young man dressed in pyjamas and a laboratory tunic.

The woman was watching him with a look of such piercing enquiry that he could not avert his gaze from her. Dressed in a cheap and brightly coloured cotton sari, she was neither young nor old, perhaps in her late thirties. When she had finished with her examination, she seated herself on the floor, with her knees drawn up in front.

Cunningham must have noticed Farley's discomfiture, for he said: 'Don't pay the slightest attention to her; she loves to stare at people.'

'Who is she?' Farley asked in an undertone.

'Oh, she's just the sweeper-woman,' Cunningham said offhandedly. Only then did Farley notice that she was holding in her hand the mark of her trade, a sweeper's jharu.

'She's a bit of a dragon,' Cunningham continued, 'been here for ever. You know what they're like: like to give visitors the once-over. Don't let her put you off; there's no harm in her.'

Farley saw her exchanging a glance with the young man who was standing beside her and he had the distinct feeling that a smile and a nod had passed between them, an almost imperceptible gesture of dismissal. Then the woman rose to her feet, turned her back on him and went over to the far corner of the room, as though to indicate that she had exhausted her interest in him.

Farley felt the blood rushing to his face.

'Don't pay her any attention;' Cunningham said to Farley, with a wink, 'she's a little touched… you know.'

He motioned to the young man to present himself. 'And this chokra-boy here,' he said with a loud satirical laugh, 'is a bearer who I've trained to help with my slides. I suppose you could call him my assistant.'

Leading the way between the laboratory's tables, Cunningham pointed to a microscope. 'You can work here,' he said to Farley. 'My bearer will get you your slides.' He allowed himself a snort of laughter as he let himself out: 'I hope you find what you are looking for.'

Farley seated himself at a microscope, and over the next hour and a half the assistant brought him several dozen slides to look at. Since the man was a menial employee Farley was not surprised that Cunningham had not taken the trouble to tell him his name. But now, as he sat watching him work, he was impressed by the young man's deftness: given his circumstances, his efficiency struck him as quite remarkable.

But the slides he presented to Farley held no surprises. They bore dry stains, and were of a familiar kind, with the black pigmented cells of malarial blood much in evidence. He had seen dozens like them as a research student in Baltimore. Of Laveran's parasite, he saw no sign whatever. Indeed, he would soon have abandoned the effort if it had not been for an odd little incident.

After he had been looking into the microscope for an hour or so, Farley grew thirsty, and asked the young assistant for water. A tumbler was duly fetched and placed in front of him. He drank half the water and, wanting to save the rest for later, placed it within easy reach, just behind his microscope.

Several minutes later, glancing away from the microscope, he made the discovery that he could see the whole room behind him, mirrored on the convex surface of the glass tumbler. He thought no more of it, but the next time he looked up his eyes were arrested by a scene that was now unfolding behind him.