I started up. Here was the missing link which I had been waiting for.
"There, at least, is the motive," I blurted out. "That is why Bernardo was so reticent. Northrop, in his innocence of heart, had showed him that inscription."
Kennedy said nothing as he finally tied up the little packet of letters and locked it in his safe. He was not given to hasty generalizations; neither was he one who clung doggedly to a preconceived theory.
It was still early in the afternoon. Craig and I decided to drop into the museum again in order to see Doctor Bernardo. He was not there and we sat down to wait.
Just then the letter box in the door clicked. It was the postman on his rounds. Kennedy walked over and picked up the letter.
The postmark bore the words, "Mexico City," and a date somewhat later than that on which Northrop had left Vera Cruz. In the lower corner, underscored, were the words, "Personal--Urgent."
"I'd like to know what is in that," remarked Craig, turning it over and over.
He appeared to be considering something, for he rose suddenly and shoved the letter into his pocket.
I followed, and a few moments later, across the campus in his laboratory, he was working quickly over an X-ray apparatus. He had placed the letter in it.
"These are what are known as 'low' tubes," he explained. "They give out 'soft rays.'" He continued to work for a few moments, then handed me the letter.
"Now, Walter," he said, "if you will just hurry back to the museum and replace that letter, I think I will have something that will astonish you--though whether it will have any bearing on the case, remains to be seen."
"What is it?" I asked, a few minutes later, when I had rejoined him, after returning the letter. He was poring intently over what looked like a negative.
"The possibility of reading the contents of documents inclosed in a sealed envelope," he replied, still studying the shadowgraph closely, "has already been established by the well-known English scientist, Doctor Hall Edwards. He has been experimenting with the method of using X-rays recently discovered by a German scientist, by which radiographs of very thin substances, such as a sheet of paper, a leaf, an insect's body, may be obtained. These thin substances through which the rays used formerly to pass without leaving an impression, can now be radiographed."
I looked carefully as he traced out something on the negative. On it was easily possible, following his guidance, to read the words inscribed on the sheet of paper inside. So admirably defined were all the details that even the gum on the envelope and the edges of the sheet of paper inside the envelope could be distinguished.
"Any letter written with ink having a mineral basis can be radiographed," added Craig. "Even when the sheet is folded in the usual way, it is possible by taking a radiograph stereoscopically, to distinguish the writing, every detail standing out in relief. Besides, it can be greatly magnified, which aids in deciphering it if it is indistinct or jumbled up. Some of it looks like mirror writing. Ah," he added, "here's something interesting!"
Together we managed to trace out the contents of several paragraphs, of which the significant parts were as follows:
I am expecting that my friend Senora Herreria will be in New York by the time you receive this, and should she call on you, I know you will accord her every courtesy. She has been in Mexico City for a few days, having just returned from Mitla, where she met Professor Northrop. It is rumored that Professor Northrop has succeeded in smuggling out of the country a very important stone bearing an inscription which, I understand, is of more than ordinary interest. I do not know anything definite about it, as Senora Herreria is very reticent on the matter, but depend on you to find out if possible and let me know of it.
According to the rumors and the statements of the senora, it seems that Northrop has taken an unfair advantage of the situation down in Oaxaca, and I suppose she and others who know about the inscription feel that it is really the possession of the government.
You will find that the senora is an accomplished antiquarian and scholar. Like many others down here just now, she has a high regard for the Japanese. As you know, there exists a natural sympathy between some Mexicans and Japanese, owing to what is believed to be a common origin of the two races.
In spite of the assertions of many to the contrary, there is little doubt left in the minds of students that the Indian races which have peopled Mexico were of Mongolian stock. Many words in some dialects are easily understood by Chinese immigrants. A secretary of the Japanese legation here was able recently to decipher old Mixtec inscriptions found in the ruins of Mitla.
Senora Herreria has been much interested in establishing the relationship and, I understand, is acquainted with a Japanese curio dealer in New York who recently visited Mexico for the same purpose. I believe that she wishes to collaborate with him on a monograph on the subject, which is expected to have a powerful effect on the public opinion both here and at Tokyo.
In regard to the inscription which Northrop has taken with him, I rely on you to keep me informed. There seems to be a great deal of mystery connected with it, and I am simply hazarding a guess as to its nature. If it should prove to be something which might interest either the Japanese or ourselves, you can see how important it may be, especially in view of the forthcoming mission of General Francisco to Tokyo.
Very sincerely yours,
DR. EMILIO SANCHEZ, Director.
"Bernardo is a Mexican," I exclaimed, as Kennedy finished reading, "and there can be no doubt that the woman he mentioned was this Senora Herreria."
Kennedy said nothing, but seemed to be weighing the various paragraphs in the letter.
"Still," I observed, "so far, the only one against whom we have any direct suspicion in the case is the shaggy Russian, whoever he is."
"A man whom Bernardo says looked like a Russian," corrected Craig.
He was pacing the laboratory restlessly.
"This is becoming quite an international affair," he remarked finally, pausing before me, his hat on. "Would you like to relax your mind by a little excursion among the curio shops of the city? I know something about Japanese curios--more, perhaps, than I do of Mexican. It may amuse us, even if it doesn't help in solving the mystery. Meanwhile, I shall make arrangements for shadowing Bernardo. I want to know just how he acts after he reads that letter."
He paused long enough to telephone his instructions to an uptown detective agency which could be depended on for such mere routine work, then joined me with the significant remark: "Blood is thicker than water, anyhow, Walter. Still, even if the Mexicans are influenced by sentiment, I hardly think that would account for the interest of our friends from across the water in the matter."
I do not know how many of the large and small curio shops of the city we visited that afternoon. At another time, I should have enjoyed the visits immensely, for anyone seeking articles of beauty will find the antique shops of Fifth and Fourth Avenues and the side streets well worth visiting.
We came, at length, to one, a small, quaint, dusty rookery, down in a basement, entered almost directly from the street. It bore over the door a little gilt sign which read simply, "Sato's."
As we entered, I could not help being impressed by the wealth of articles in beautiful cloisonne enamel, in mother-of-pearl, lacquer, and champleve. There were beautiful little koros, or incense burners, vases, and teapots. There were enamels incrusted, translucent, and painted, works of the famous Namikawa, of Kyoto, and Namikawa, of Tokyo. Satsuma vases, splendid and rare examples of the potter's art, crowded gorgeously embroidered screens depicting all sorts of brilliant scenes, among others the sacred Fujiyama rising in the stately distance. Sato himself greeted us with a ready smile and bow.
"I am just looking for a few things to add to my den," explained Kennedy, adding, "nothing in particular, but merely whatever happens to strike my fancy."
"Surely,