Ambler Jevons read the letter, then handed it to me without comment.

It was written upon the note-paper I knew so well, stamped with the neat address “Neneford,” in black, but bearing no date. What I read was as follows:—

“Ah!” I exclaimed. “Then he warned her, and she misunderstood his intention.”

“Without a doubt,” said Ambler, taking the letter from my hand. “This was written probably only a few days before her death. That man,” and he glanced at the prostrate body, “was the only one who could give us the clue by which to unravel the mystery.”

But the dead man’s lips had closed, and his secret was held for ever. Only those letters remained to connect him with the river tragedy; or rather to show that he had communicated with the unfortunate Mrs. Courtenay.

In company we walked to Leman Street Police Station, one of the chief centres of the Metropolitan Police in the East End, and there, in an upper office, Ambler had a long consultation with the sergeant of the Criminal Investigation Department.

I described the appearance of the body, and stated my suspicions of poisoning, all of which the detective carefully noted before going forth to make his own examination. My address was taken, so that I might assist at the post-mortem, and then, shortly after midnight I drove back westward through the City with Ambler at my side.

He spoke little, and when in Oxford Street, just at the corner of Newman Street, he descended, wished me a hurried good-night, and disappeared into the darkness. He was often given to strange vagaries of erratic movement. It was as though some thought had suddenly occurred to him, and he acted at once upon it.

That night I scarcely closed my eyes. My brain was awhirl with thoughts of all the curious events of the past few months—the inexplicable presence of old Mr. Courtenay, and the subsequent death of Mary and of the only man who, according to Ambler, knew the remarkable secret.

Ethelwynn’s strange words worried me. What could she mean? What did she know? Surely hers could not be a guilty conscience. Yet, in her words and actions I had detected that cowardice which a heavy conscience always engenders. One by one I dissected and analysed the Seven Secrets, but not in one single instance could I obtain a gleam of the truth.

While at the hospital next day I was served with a notice to assist at the post-mortem of the unfortunate Lane, whose body was lying in the Shadwell mortuary; and that same afternoon I met by appointment Doctor Tatham, of the London Hospital, who, as is well known, is an expert toxicologist.

To describe in technical detail the examination we made would not interest the general reader of this strange narrative. The average man or woman knows nothing or cares less for the duodenum or the pylorus; therefore it is not my intention to go into long and wearying detail. Suffice it to say that we preserved certain portions of the body for subsequent examination, and together were engaged the whole evening in the laboratory of the hospital. Tatham was well skilled in the minutiÆ of the tests. The exact determination of the cause of death in cases of poisoning always depends partly on the symptoms noted before death, and partly on the appearances found after death. Regarding the former, neither of us knew anything; hence our difficulties were greatly increased. The object of the analyst is to obtain the substances which he has to examine chemically in as pure a condition as possible, so that there may be no doubt about the results of his tests; also, of course, to separate active substances from those that are inert, all being mixed together in the stomach and alimentary canal. Again, in dealing with such fluids as the blood, or the tissues of the body, their natural constituents must be got rid of before the foreign and poisonous body can be reached. There is this difficulty further to contend with: that some of the most poisonous of substances are of unstable composition and are readily altered by chemical reagents; to this group belong many vegetable and most animal poisons. These, therefore, must be treated differently from the more stable inorganic compounds. With an inorganic poison we may destroy all organic materials mixed with it, trusting to find the poison still recognisable after this process. Not so with an organic substance; that must be separated by other than destructive means.

Through the whole evening we tested for the various groups of poisons—corrosives, simple irritants, specific irritants and neurotics. It was a long and scientific search.

Some of the tests with which I was not acquainted I watched with the keenest interest, for, of all the medical men in London, Tatham was the most up to date in such analyses.

At length, after much work with acids, filtration, and distillation, we determined that a neurotic had been employed, and that its action on the vasomotor system of the nerves was very similar, if not identical, with nitrate of amyl.

Further than that, even Tatham, expert in such matters, could not proceed. Hours of hard work resulted in that conclusion, and with it we were compelled to be satisfied.In due course the inquest was held at Shadwell, and with Ambler I attended as a witness. The reporters, of course, expected a sensation; but, on the contrary, our evidence went to show that, as the poisonous substance was found in the “quartern” bottle on deceased’s table, death was in all probability due to suicide.

Some members of the jury took an opposite view. Then the letters we had found concealed were produced by the police, and, of course, created a certain amount of interest. But to the readers of newspapers the poisoning of a costermonger at Shadwell is of little interest as compared with a similar catastrophe in that quarter of London vaguely known as “the West End.” The letters were suspicious, and both coroner and jury accepted them as evidence that Lane was engaged upon an elaborate scheme of blackmail.

“Who is this Mary Courtenay, who writes to him from Neneford?” inquired the coroner of the inspector.

“Well, sir,” the latter responded, “the writer herself is dead. She was found drowned a few days ago near her home under suspicious circumstances.”

Then the reporters commenced to realize that something extraordinary was underlying the inquiry.

“Ah!” remarked the coroner, one of the most acute officials of his class. “Then, in face of this, her letter seems to be more than curious. For aught we know the tragedy at Neneford may have been wilful murder; and we have now the suicide of the assassin?”“That, sir, is the police theory,” replied the inspector.

“Police theory be hanged!” ejaculated Ambler, almost loud enough to be heard. “The police know nothing of the case, and will never learn anything. If the jury are content to accept such an explanation, and brand poor Lane as a murderer, they must be allowed to do so.”

I knew Jevons held coroners’ juries in the most supreme contempt; sometimes rather unreasonably so, I thought.

“Well,” the coroner said, “this is certainly remarkable evidence,” and he turned the dead woman’s letter over in his hand. “It is quite plain that the deceased approached the lady ostensibly to give her warning of some danger, but really to blackmail her; for what reason does not at present appear. He may have feared her threat to give information to the police; hence his crime, and subsequent suicide.”

“Listen!” exclaimed Jevons in my ear. “They are actually trying the dead man for a crime he could not possibly have committed! They’ve got hold of the wrong end of the stick, as usual. Why don’t they give a verdict of suicide and have done with it. We can’t afford to waste a whole day explaining theories to a set of uneducated gentlemen of the Whitechapel Road. The English law is utterly ridiculous where coroners’ juries are concerned.”

The coroner heard his whispering, and looked towards us severely.“We have not had sufficient time to investigate the whole of the facts connected with Mrs. Courtenay’s mysterious death,” the inspector went on. “You will probably recollect, sir, a mystery down at Kew some little time ago. It was fully reported in the papers, and created considerable sensation—an old gentleman was murdered under remarkable circumstances. Well, sir, the gentleman in question was Mrs. Courtenay’s husband.”

The coroner sat back in his chair and stared at the officer who had spoken, while in the court a great sensation was caused. Mention of the Kew Mystery brought its details vividly back to the minds of everyone. Yes. After all, the death of that poor costermonger, Lanky Lane, was of greater public interest than the representatives of the Press anticipated.

“Are you quite certain of this?” the coroner queried.

“Yes, sir. I am here by the direction of the Chief Inspector of Scotland Yard to give evidence. I was engaged upon the case at Kew, and have also made inquiries into the mystery at Neneford.”

“Then you have suspicion that the deceased was—well, a person of bad character?”

“We have.”

“Fools!” growled Ambler. “Lane was a policeman’s ‘nose,’ and often obtained payment from Scotland Yard for information regarding the doings of a certain gang of thieves. And yet they actually declare him to be a bad character. Preposterous!”“Do you apply for an adjournment?”

“No, sir. We anticipate that the verdict will be suicide—the only one possible in face of the evidence.”

And then, as though the jury were compelled to act upon the inspector’s suggestion, they returned a simple verdict. “That the deceased committed suicide by poisoning while of unsound mind.”