“My God!” cried Innes, “here is proof that the chief was right!”  
Wessex nodded in silent agreement. On the table lay the report of Merton, the analyst, concerning the stains upon the serviette which Harley had sent from the house of the late Sir Charles Abingdon. Briefly, it stated that the serviette had been sprinkled with some essential oil, the exact character of which Merton had found himself unable to determine, its perfume, if it ever possessed any, having disappeared. And the minute quantity obtainable from the linen rendered ordinary tests difficult to apply. The analyst’s report, however, concluded as follows:
 
“Mr. Harley, having foreseen these difficulties, and having apparently suspected that the oil was of Oriental origin, recommended me, in the note which he enclosed with the serviette, to confer with Dr. Warwick Grey. I send a copy of a highly interesting letter which I have received from Doctor Grey, whose knowledge of Eastern poison is unparalleled, and to whose opinion I attach immense importance.”
 
It was the contents of this appended letter which had inspired Innes’s remarks. Indeed, it contained matter which triumphantly established Paul Harley’s theory that Sir Charles Abingdon had not died from natural causes. The letter was as follows:
 
‘No.—— Harley Street London, W. I.
 
‘MY DEAR MERTON:
 
‘I am indebted to you and to Mr. Harley for an opportunity of examining the serviette, which I return herewith. I agree that the oil does not respond to ordinary tests, nor is any smell perceptible. But you have noticed in your microscopic examination of the stains that there is a peculiar crystalline formation upon the surface. You state that this is quite unfamiliar to you, which is not at all strange, since outside of the Himalayan districts of Northwest India I have never met with it myself.
 
‘Respecting the character of the oil employed, however, I am in no doubt, and I actually possess a dried specimen of the flower from which it is expressed. This is poetically known among the Mangars, one of the fighting tribes of Nepal, as the Bloom or Orchid of Sleep.
 
‘It is found upon the lower Himalayan slopes, and bears a close resemblance to the white odontoglossum of commerce, except that the flower is much smaller. Its perfume attracts insects and sometimes small animals and reptiles, although inhalation seems to induce instant death. It may be detected in its natural state by the presence of hundreds of dead flies and insects upon the ground surrounding the plant. It is especially fatal to nocturnal insects, its perfume being stronger at night.
 
‘Preparation of the oil is an art peculiar to members of an obscure sect established in that district, by whom it is said to be employed for the removal of enemies.
 
‘An article is sprinkled with it, and whilst the perfume, which is reported to resemble that of cloves, remains perceptible, to inhale it results in immediate syncope, although by what physiological process I have never been enabled to determine.
 
‘With the one exception which I have mentioned, during my stay in Nepal and the surrounding districts I failed to obtain a specimen of this orchid. I have twice seen the curious purple stain upon articles of clothing worn by natives who had died suddenly and mysteriously. The Mangars simply say, “He has offended someone. It is the flower of sleep.”
 
‘I immediately recognized the colour of the stains upon the enclosed serviette, and also the curious crystalline formation on their surface. The identity of the “someone” to whom the Mangars refer, I never established. I shall welcome any particulars respecting the history of the serviette.
 
‘Very truly yours,
 
‘WARWICK GREY.’
 
“Sir Charles Abingdon was poisoned,” said Wessex in a hushed voice. “For the girl’s sake I hate the idea, but we shall have to get an exhumation order.”
 
“It is impossible,” returned Innes, shortly. “He was cremated.”
 
“Good heavens,” murmured Wessex, “I never knew.”
 
“But after all,” continued Inures, “it is just as well for everyone concerned. The known facts are sufficient to establish the murder, together with the............