This reminds me of an experience I had a few years back, when I was in my early 40s. It was just before dawn one day, probably around 6:00 a.m., on a popular asphalt running path, not very well lit, and I was quickly reeling in a runner that was a couple of hundred yards up ahead of me. As I got closer, I saw him look back and then suddenly pick up his pace. He looked to be a guy in his early 20s. I continued closing in on him, having picked up my pace as well, instinctively feeling the challenge. He proceeded to take a turn onto a lesser-run branch off of the major path, so I figured, what the heck, I'll call his bluff, and turned there as well, probably now within 10 yards of the guy. It was quite dark on this path, but I had run it many times, and knew it quite well. About 100 yards down the path, it made a 90 degree left-hand turn, and when we approached it, the guy proceeded to run straight off the path into the woods, into complete darkness! I continued to run the path, right past where he disappeared, but had later wondered, did he run off the path into the woods because he didn't know that the path turned there? or to cop out of the challenge without being passed, thus "saving face"? or maybe to go where he had planned to go all along (some obscure off-the-trail course he knew)? or perhaps because he thought he was being stalked? Regardless of his reason, it certainly caught me by surprise, and in retrospect, it was a really weird interaction that had occurred between us.