I was up on the interstate in just a few minutes, then quickly north to I-75. As you head west on 75 the city gradually thins away. Then there is one final furious explosion of strip malls and houses just before the toll booth for Alligator Alley. At the booth I pulled over and called the number again. The same neutral female voice gave me a set of coordinates and the line went dead. I took it to mean that they were no longer moving.

According to the map, Sergeant Doakes and Dr. Danco were now settling comfortably into the middle of an unmarked watery wilderness about forty miles ahead of me. I didn’t know about Danco, but I didn’t think Doakes would float very well. Perhaps the GPS could lie after all. Still, I had to do something, so I pulled back onto the road, paid my toll, and continued westward.

At a spot parallel to the location on the GPS, a small access road branched off to the right. It was nearly invisible in the dark, especially since I was traveling at seventy miles per hour. But as I saw it whiz past I braked to a stop on the shoulder of the road and backed up to peer at it. It was a one-lane dirt road that led nowhere, up over a rickety bridge and then straight as an arrow into the darkness of the Everglades. In the headlights of the passing cars I could only see about fifty yards down the road, and there was nothing to see. A patch of knee-high weeds grew up in the center of the road between the two deeply rutted tire tracks. A clump of short trees hung over the road at the edge of darkness, and that was it.

I thought about getting out and looking for some kind of clue, until I realized how silly that was. Did I think I was Tonto, faithful Indian guide? I couldn’t look at a bent twig and tell how many white men had been past in the last hour. Perhaps Dexter’s dutiful but uninspired brain pictured him as Sherlock Holmes, able to examine the wheel ruts and deduce that a left-handed hunchback with red hair and a limp had gone down the road carrying a Cuban cigar and a ukelele. I would find no clues, not that it mattered. The sad truth was, this was either it or I was all done for the night, and Sergeant Doakes was done for considerably longer.

Just to be absolutely sure—or at any rate, absolutely free of guilt—I called Doakes’s top secret telephone number again. The voice gave me the same coordinates and hung up; wherever they were, they were still there, down this dark and dirty little road.

I was apparently out of choices. Duty called, and Dexter must answer. I turned the wheel hard and started down the road.