This novel manner of traveling, although it kept off vagrant militia, had its sinister features for the timid members of the party. Mrs. Quayle, whose fear of a burro grew in proportion as she became familiar with that harmless and necessary animal, believed that she and her friends had fallen captives, through a skillful bit of strategy, into the enemy's hands and were being led either to their death or imprisonment. To this belief she stuck, in spite of the vehemence and ridicule with which Doctor Miranda seasoned his arguments against it. Indeed, had she dared express her full opinion her suspicions would have involved the Doctor himself, whose explosive habits and other eccentricities kept her in a continual state of alarm that was increased, every now and then, by his malicious allusions to the jewelry she wore. Andrew, inclined to attribute his fever to the famous pills and the heroic treatment to which he had been subjected, secretly shared her feeling, and was in hourly dread of some new calamity striking him from the same quarter. Harold Leighton and Una, however, were too much absorbed in David's mysterious fate to be greatly concerned by what was going on immediately around them. The old savant, unable to explain the disaster, was distressed beyond measure by the poignant grief of his niece. In his own mind he was convinced that the singular occurrence on the Honda road was related in some way to David's former disappearance, and this belief stimulated his professional eagerness to solve the puzzle presented by so strange a coincidence. Una's appeal, therefore, to go any length in the rescue of David needed no urging. It was met with a hearty promise of aid from Doctor Miranda, who stormed at the government, in and out of season, for permitting bands of peons to endanger the lives of harmless travelers. The Doctor was especially indignant with Herran, who called upon the Americans before they were fairly settled in their hotel in Bogota. He pitched into this hapless officer with his choicest bits of vituperation, until Herran began to think that the loss of one man, under certain circumstances, was as serious an affair as the loss of an isthmus. Leighton, however, did not share Doctor Miranda's views of the matter. "Miranda is unreasonable," he said to Herran. "There is a mystery in this case. You have done all you could to save the young man, and you are now offering to help us." "That is right! That is right!" agreed Miranda. "We must find him." "Anything I can do----" volunteered Herran. "Do you know an American in this town by the name of Raoul Arthur?" interrupted Leighton. "How not! But--I don't like him." "Never mind. I must see him. If any one can unravel this thing, he can." "Mr. Meudon spoke of him. I will find him for you." "Do you know where he lives?" "Surely, Senor. In the Calle Mercedes." "Take me to him."