"Down on that road which leads to the Rio Grande. There was a fellow talking to a ranchman I've met several times, a Texan named Lawson. As soon as he saw me he took to his heels. I questioned Lawson about him and he said the fellow had come across the river at a point about a quarter of a mile below here." Dave listened to this explanation with interest, and immediately sought out Mr. Obray. The upshot of the talk was that our hero was given permission to leave the camp for the day, taking Roger with him. The two chums went off armed with their pistols, not knowing what might happen. They first walked to where Roger had met the ranchman, and there the senator's son pointed out the direction that the young man who had run away had taken. They followed this trail, and presently reached the roadway which ran in sight of the river. There were comparatively few craft on the stream, and none of these looked as if it might be occupied by the young man they were after. But presently they reached a small creek flowing into the Rio Grande, and on this saw two flat-bottomed rowboats. "There he is now!" exclaimed Dave, suddenly, and pointed to the first of the rowboats, which was being sent down the creek in the direction of the river. The sole occupant of the craft was the fellow at the oars, and the two chums readily made out that it was the former moving-picture actor. As soon as he made certain of Porton's identity, Dave pulled Roger down in the tall grass which bordered the creek. "There is no use in letting him see us," explained our hero. "Do you suppose he is bound for the Mexican shore?" questioned the senator's son. "More than likely, Roger." Dave looked questioningly at his chum. "Are you game to follow him?" he added. "What do you mean?" "We might take that other rowboat and go after him. I see it contains a pair of oars. Either of us ought to be able to row as well as Porton, and if we can catch him before he lands maybe we'll be able to drive him back to the United States side of the river." "All right, I'll go with you," responded Roger, quickly. "Come ahead!" and he started on a run for the rowboat. The craft was tied fast to two stakes, but it was an easy matter for them to loosen the ropes. This done, Dave took up the oars, shoved off, and started to row with all the strength at his command. Evidently Ward Porton had not expected to be followed, for he was rowing leisurely, allowing his flat-bottomed boat to drift with the current. He was much surprised when he saw the other boat come on at a good rate of speed. "Get back there!" he yelled, when he recognized the occupants of the second craft. "Get back, I tell you, or I'll shoot!" "If you do we'll do some shooting on our own account, Porton!" called back Roger, and showed his pistol. The sight of the weapon evidently frightened Porton greatly. Yet he did not cease rowing, and now he headed directly for the Mexican shore.