Loveday evidently had had some difficulty in finding a messenger for this note, for it was brought by a gardener's boy, who informed Griffiths that the lady had said he would receive a gold sovereign if he delivered the letter all right.
  Griffiths paid the boy and dismissed him, and then proceeded to read Loveday's communication.
  It was written hurriedly in pencil, and ran as follows:
Things are getting critical here. Directly you receive this, come up to the house with
two of your men, and post yourselves anywhere in the grounds where you can see
and not be seen. There will be no difficulty in this, for it will be dark by the time
you are able to get there. I am not sure whether I shall want your aid to-night,
but you had better keep in the grounds until morning, in case of need; and above
all, never once lose sight of the study window. [This was underscored.] If I
put a lamp with a green shade in one of those windows, do not lose a moment in
entering by that window, which I will contrive to keep unlocked.
Detective Griffiths rubbed his forehead â rubbed his eyes, as he finished reading this.
  'Well, I daresay it's all right,' he said, 'but I'm bothered, that's all, and for the life of me I can't see one step of the way she is going.'
  He looked at his watch; the hands pointed to a quarter past six. The short September day was drawing rapidly to a close. A good five miles lay between him and Troyte's Hill â there was evidently not a moment to lose.
  At the very moment that Griffiths, with his two constables, were once more starting along the Grenfell High Road behind the best horse they could procure, Mr Craven was rousing himself from his long slumber, and beginning to look around him. That slumber, however, though long, had not been a peaceful one, and it was sundry of the old gentleman's muttered exclamations, as he had started uneasily in his sleep, that had caused Loveday to pen, and then to creep out of the room to despatch, her hurried note.
  What effect the occurrence of the morning had had upon the household generally, Loveday, in her isolated corner of the house, had no means of ascertaining. She only noted that when Hales brought in her tea, as he did precisely at five o'clock, he wore a particularly ill-tempered expression of countenance, and she heard him mutter, as he set down the tea-tray with a clatter, something about being a respectable man, and not used to such 'goings on'.
  It was not until nearly an hour and a half after this that Mr Craven had awakened with a sudden start, and, looking wildly around him, had questioned Loveday who had entered the room.
  Loveday explained that the butler had brought in lunch at one, and tea at five, but that since then no one had come in.
  'Now that's false,' said Mr Craven, in a sharp, unnatural sort of voice; 'I saw him sneaking round the room, the whining, canting hypocrite, and you must have seen him, too! Didn't you hear him say, in his squeaky old voice: "Master, I knows your secret â ."' He broke off abruptly, looking wildly round. 'Eh, what's this?' he cried. 'No, no, I'm all wrong â Sandy is dead and buried â they held an inquest on him, and we all praised him up as if he were a saint.'
  'He must have been a bad man, that old Sandy,' said Loveday sympathetically.
  'You're right! you're right!' cried Mr Craven, springing up excitedly from his chair and seizing her by the hand. 'If ever a man deserved his death, he did. For thirty years he held that rod over my head, and then â ah where was I?'
  He put his hand to his head and again sank, as if exhausted, into his chair.
  'I suppose it was some early indiscretion of yours at college that he knew of?' said Loveday, eager to get at as much of the truth as possible while the mood for confidence held sway in the feeble brain.
  'That was it! I was fool enough to marry a disreputable girl â a barmaid in the town â and Sandy was present at the wedding, and then â .' Here his eyes closed again and his mutterings became incoherent.
  For ten minutes he lay back in his chair, muttering thus; 'A yelp â a groan,' were the only words Loveday could distinguish among those mutterings, then, suddenly, slowly and distinctly, he said, as if answering some plainly-put question: 'A good blow with the hammer and the thing was done.'
  'I should like amazingly to see that hammer,' said Loveday; 'do you keep it anywhere at hand?'
  His eyes opened with a wild, cunning look in them.
  'Who's talking about a hammer? I did not say I had one. If anyone says I did it with a hammer, they're telling a lie.'
  'Oh, you've spoken to me about the hammer two or three times,' said Loveday calmly; 'the one that killed your dog, Captain, and I should like to see it, that's all.'
  The look of cunning died out of the old man's eye â 'Ah, poor Captain! Splendid dog that! Well, now, where were we? Where did we leave off? Ah, I remember, it was the elemental sounds of speech that bothered me so that night. Were you here then? Ah, no! I remember. I had been trying all day to assimilate a dog's yelp of pain to a human groan, and I couldn't do it. The idea haunted me â followed me about wherever I went. If they were both elemental sounds, they must have something in common, but the link between them I could not find; then it occurred to me, would a well-bred, well-trained dog like my Captain in the stables, there, at the moment of death give an unmitigated currish yelp; would there not be something of a human note in his death-cry? The thing was worth putting to the test. If I could hand down in my treatise a fragment of fact on the matter, it would be worth a dozen dogs' lives. So I went out into the moonlight â ah, but you know all about it â now, don't you?'
  'Yes. Poor Captain! Did he yelp or groan?'
  'Why, he gave one loud, long, hideous yelp, just as if he had been a common cur. I might just as well have let him alone; it only set that other brute opening his window and spying out on me, and saying in his cracked old voice: "Master, what are you doing out here at this time of night?"'
  Again he sank back in his chair, muttering incoherently with halfclosed eyes.
  Loveday let him alone for a minute or so; then she had another question to ask.
  'And that other brute â did he yelp or groan when you dealt him his blow?'
  'What, old Sandy â the brute? He fell back â Ah, I remember, you said you would like to see the hammer that stopped his babbling old tongue â now, didn't you?'
  He rose a little unsteadily from his chair, and seemed to drag his long limbs with an effort across the room to a cabinet at the farther end. Opening a drawer in this cabinet, he produced, from amidst some specimens of strata and fossils, a large-sized geological hammer.
  He brandished it for a moment over his head, then paused with his finger on his lip.
  'Hush!' he said, 'we shall have the fools creeping in to peep at us if we don't take care.' And to Loveday's horror he suddenly made for the door, turned the key in the lock, withdrew it and put it into his pocket.
  She looked at the clock; the hands pointed to half-past seven. Had Griffiths received her note at the proper time, and were the men now in the grounds? She could only pray that they were.
  'The light is too strong for my eyes,' she said, and rising from her chair, she lifted the green-shaded lamp and placed it on a table that stood at the window.
  'No, no, that won't do,' said Mr Craven; 'that would show everyone outside what we're doing in here.' He crossed to the window as he spoke and removed the lamp thence to the mantelpiece.
  Loveday could only hope that in the few seconds it had remained in the window it had caught the eye of the outside watchers.
  The old man beckoned to Loveday to come near and examine his deadly weapon. 'Give it a good swing round,' he said, suiting the action to the word, 'and down it comes with a splendid crash.' He brought the hammer round within an inch of Loveday's forehead.
  She started back.
  'Ha, ha,' he laughed harshly and unnaturally, with the light of madness dancing in his eyes now; 'did I frighten you? I wonder what sort of sound you would make if I were to give you a little tap just there.' Here he lightly touched her forehead with the hammer. 'Elemental, of course, it would be, and â .'
  Loveday steadied her nerves with difficulty. Locked in with this lunatic, her only chance lay in gaining time for the detectives to reach the house and enter through the window.
  'Wait a minute,' she said, striving to divert his attention; 'you have not yet told me what sort of an elemental sound old Sandy made when he fell. If you'll give me pen and ink, I'll write down a full account of it all, and you can incorporate it afterwards in your treatise.'
  For a moment a look of real pleasure flitted across the old man's face, then it faded. 'The brute fell dead without a sound,' he answered; 'it was all for nothing, that night's work; yet not altogether for nothing. No, I don't mind owning I would do it all over again to get the wild thrill of joy at my heart that I had when I looked down into that old man's dead face and felt myself free at last! Free at last!' His voice rang out excitedly â once more he brought his hammer round with an ugly swing.
  'For a moment I was a young man again; I leaped into his room â the moon was shining full in through the window â I thought of my old college days, and the fun we used to have at Pembroke â topsy turvey I turned everything â .' He broke off abruptly, and drew a step nearer to Loveday. 'The pity of it all was,' he said, suddenly dropping from his high, excited tone to a low, pathetic one, 'that he fell without a sound of any sort.' Here he drew another step nearer. 'I wonder â ' he said, then broke off again, and came close to Loveday's side. 'It has only this moment occurred to me,' he said, now with his lips close to Loveday's ear, 'that a woman, in her death agony, would be much more likely to give utterance to an elemental sound than a man.'
  He raised his hammer, and Loveday fled to the window, and was lifted from the outside by three strong pairs of arms.
******
'I thought I was conducting my very last case â I never had such a narrow escape before!' said Loveday, as she stood talking with Mr Griffiths on the Grenfell platform, awaiting the train to carry her back to London. 'It seems strange that no one before suspected the old gentleman's sanity â I suppose, however, people were so used to his eccentricities that they did not notice how they had deepened into positive lunacy. His cunning evidently stood him in good stead at the inquest.'
  'It is possible,' said Griffiths thoughtfully, 'that he did not absolutely cross the very slender line that divides eccentricity from madness until after the murder. The excitement consequent upon the discovery of the crime may just have pushed him over the border. Now, Miss Brooke, we have exactly ten minutes before your train comes in. I should feel greatly obliged to you if you would explain one or two things that have a professional interest for me.'
  'With pleasure,' said Loveday. 'Put your questions in categorical order and I will answer them.'
  'Well, then, in the first place, what suggested to your mind the old man's guilt?'
  'The relations that subsisted between him and Sandy seemed to me to savour too much of fear on the one side and power on the other. Also the income paid to Sandy during Mr Craven's absence in Natal bore, to my mind, an unpleasant resemblance to hush-money.'
  'Poor wretched being! And I hear that, after all, the woman he married in his wild young days died soon afterwards of drink. I have no doubt, however, that Sandy sedulously kept up the fiction of her existence, even after his master's second marriage. Now for another question: how was it you knew that Miss Craven had taken her brother's place in the sick-room?'
  'On the evening of my arrival I discovered a rather long lock of fair hair in the unswept fireplace of my room, which, as it happened, was usually occupied by Miss Craven. It at once occurred to me that the young lady had been cutting off her hair and that there must be some powerful motive to induce such a sacrifice. The suspicious circumstances attending her brother's illness soon supplied me with such a motive.'
  'Ah! that typhoid fever business was very cleverly done. Not a servant in the house, I verily believe, but who thought Master Harry was upstairs, ill in bed, and Miss Craven away at her friends' in Newcastle. The young fellow must have got a clear start off within an hour of the murder. His sister, sent away the next day to Newcastle, dismissed her maid there, I hear, on the plea of no accommodation at her friends' house â sent the girl to her own home for a holiday and herself returned to Troyte's Hill in the middle of the night, having walked the five miles from Grenfell. No doubt her mother admitted her through one of those easily-opened front windows, cut her hair and put her to bed to personate her brother without delay. With Miss Craven's strong likeness to Master Harry, and in a darkened room, it is easy to understand that the eyes of a doctor, personally unacquainted with the family, might easily be deceived. Now, Miss Brooke, you must admit that with all this elaborate chicanery and double dealing going on, it was only natural that my suspicions should set in strongly in that quarter.'
  'I read it all in another light, you see,' said Loveday. 'It seemed to me that the mother, knowing her son's evil proclivities, believed in his guilt, in spite, possibly, of his assertion of innocence. The son, most likely, on his way back to the house after pledging the family plate, had met old Mr Craven with the hammer in his hand. Seeing, no doubt, how impossible it would be for him to clear himself without incriminating his father, he preferred flight to Natal to giving evidence at the inquest.'