these same readers, for I hold in this hand several threads of one of the strangest cases which ever perplexed a man’s brain, and yet I lack the one or two which are needful to complete my theory. But I’ll have them, Watson, I’ll have them!’ His eyes kindled and a slight flush sprang into his thin cheeks. For an instant the veil had lifted upon his keen, intense nature, but for an instant only. When I glanced again his face had resumed that Red Indian composure which had made so many regard him as a machine rather than a man.

‘The problem presents features of interest,’ said he; ‘I may even say very exceptional features of interest. I have already looked into the matter, and have come, as I think, within sight of my solution. If you could accompany me in that last step, you might be of considerable service to me.’

‘I should be delighted.’

‘Could you go as far as Aldershot to-morrow?’

‘I have no doubt Jackson would take my practice.’

‘Very good. I want to start by the 11.10 from Waterloo.’

‘That would give me time.’

‘Then, if you are not too sleepy, I will give you a sketch of what has happened and of what remains to be done.’

‘I was sleepy before you came. I am quite wakeful now.’

‘I will compress the story as far as may be done without omitting anything vital to the case. It is conceivable that you may even have read some account of the matter. It is the supposed murder of Colonel Barclay, of the Royal Mallows, at Aldershot, which I am investigating.’

‘I have heard nothing of it.’

‘It has not excited much attention yet, except locally. The facts are only two days old. Briefly they are these:

‘The Royal Mallows is, as you know, one of the most famous Irish regiments in the British Army. It did wonders both in the Crimea and the Mutiny, and has since that time distinguished itself upon every possible occasion. It was commanded up to Monday night by James Barclay, a gallant veteran, who started as a full private, was raised to commissioned rank for his bravery at the time of the Mutiny, and so lived to command the regiment in which he had once carried a musket.

‘Colonel Barclay had married at the time when he was a sergeant, and his wife, whose maiden name was Miss Nancy Devoy, was the daughter of a former colour-sergeant in the same corps. There was, therefore, as can be imagined, some little social friction when the young couple (for they were still young) found themselves in their new surroundings. They appear, however, to have quickly adapted themselves, and Mrs Barclay has always, I understand, been as popular with the ladies of the regiment as her husband was with his brother officers. I may add that she was a woman of great beauty, and that even now, when she has been married for upwards of thirty years, she is still of a striking appearance.

‘Colonel Barclay’s family life appears to have been a uniformly happy one. Major Murphy, to whom I owe most of my facts, assures me that he has never heard of any misunderstanding between the pair. On the whole he thinks that Barclay’s devotion to his wife was greater than his wife’s to Barclay. He was acutely uneasy if he were absent from her for a day. She, on the other hand, though devoted and faithful, was less obtrusively affectionate. But they were regarded in the regiment as the very model of a middle-aged couple. There was absolutely nothing in their mutual relations to prepare people for the tragedy which was to follow.