Of course the secret of the White Envelope was not confided even to her most intimate friends. This correspondence having been fairly established, there was nothing to prevent Hansie from using the European mail every week; but to avoid needless risks and the possible exposure of the valuable secret, it was agreed to use it only in cases of extreme necessity. The sign of the White Envelope became an understood thing between the conspirators, and for all other correspondence grey and coloured envelopes were used. The correspondent in the north of Holland was a young minister of the Gospel who had taken for years an unusual interest in Hansie's career. At this point of our story the two young people, after some years of estrangement, brought about by an unfortunate misunderstanding on his part, pride and self-will on hers, had reached the delightfully unsettling stage of exchanging photographs, the sequel of which took place under the most romantic circumstances, not to be related in this volume. "It is an ill wind that blows nobody any good," the young man must often have thought, as he faithfully carried out every instruction from the scene of action. All communications for the President and Dr. Leyds were sent to him (through the White Envelope), because it was not considered safe to correspond with them direct, even through the medium of the lemon-juice discovery. As time went on, this method of communication was used for many purposes and always with success, but some time after the war, when it was Hansie's right and privilege to go through the war correspondence of the young minister of religion, she came upon a letter from Dr. Leyds to him, in which she read, with growing interest, the following information: "I cannot conceal from you that I was startled when I opened the last white envelope, for I was able to read the whole report, though the writing was faint, without applying the heating process to it. Perhaps this letter lay in a warm place near the engine-rooms on the voyage. Will you not send a timely warning? You could, for instance, say that the measles have come out and are plainly visible, even without the application of hot compresses. Those people are quite clever enough to understand what you wish to convey to them." This warning did not reach Harmony at the time. Perhaps the censor, trained as he must have been in the art of reading dangerous meanings into seemingly harmless sentences, decided in his own mind that it would be advisable to keep the information about the measles to himself, and consigned the letter to the waste-paper basket. In time experience taught the conspirators at Harmony that the greatest care would be necessary in the use of the White Envelope, and to this they probably owe the fact that it was never found out by the enemy.