Many thanks, everyone, for the kind words. At this point I've recovered from the shock of nearly losing Dickens, but I have to admit to some trepidations for the future. It's sad to think I won't be able to let him run off-leash on our walks, especially since, with those two strange exceptions, he has always been so perfectly under my control; coming to me the instant I call him, and following directions as to where I want him to go. But if he does this again, especially on the other side of the highway, things might not work out so well.
I'm going to take an excursion out to that one area some time soon and see if I can determine just what it was that spooked him so. It's just a small wooded area at the bottom of a hill behind the Governor's Mansion in Dover. A narrow river cuts through the area; on the far side is a sliver of public park area, but few people ever go across to the near side, since there's no bridge or other means of getting there. In the past six months, some vagrant just dumped a large pile of personal effects in the woods on that side, including toiletries, papers and clothes. The first time Dickens got spooked I had held up a flannel shirt that was part of that junk pile. He took one look at it and then started running off in the direction we had come from; I found him about a quarter-mile away, acting as if he were looking for me.
I thought it was a one-off thing; that perhaps the sight of me holding that shirt made him think I was someone else. The past three or four weeks I've taken him out there with no further incidents, and thought we'd have no more trouble. But yesterday, I paused because amongst the junk the vagrant had left was an official-looking paper bearing the letterhead of a local attorney. Perhaps, I thought, I could discover the vagrant's name. I stopped to read, and a minute later, when I looked up, Dickens was well past me, apparently "spooked" again.
Interestingly, the letter I read was for the attorney to inform his client that he would be unable to effect a reduction in the sentence he was about to be given for burglary and that he would most likely be sentenced to three years on each count of a number of charges related to his crime. Assuming that the client and the vagrant are the same, I believe he is at present either a fugitive from justice or serving a lengthy prison term.
Which, of course, does nothing to tell me why Dickens would get spooked on two separate occasions in that one area, to the point where he wouldn't recognize his master, and felt the need to get away. That's what I need to find out!