They Were Watching for Danger. She Was Watching for Cause.

Rex, the Belgian Malinois with the scarred muzzle, was pacing when I reached the fence. Twelve feet down. Pivot. Twelve feet back. Pivot. His eyes were the kind of eyes that processed everything in a space at once — entrances, positions, threats, anomalies — and they swept across me and filed me and swept away again without a change in his pacing rhythm.

Kilo, the German Shepherd who used to work children's hospital visits, lay flat with his muzzle on his paws and his eyes open and pointed at nothing that existed in this kennel.

Dax, the youngest Malinois, stood in the back corner of his run with his body rigid and his attention divided between everything simultaneously.

I watched Rex first.

Twelve feet. Pivot.

At the north end of the run, his head dipped every time. Not much. A fraction. But it was consistent — not a choice, not a behavior, but a response to something that existed at that end of the run.

"What's behind that wall?" I asked.

Hewitt blinked. He told me it was an old supply corridor. Closed for about a year. I asked whether air moved through it. He didn't know.

I watched Rex pivot again. Head drop. Turn. Resume.

"There's something coming through that wall," I said. "A sound or a scent. It resets him every time he reaches that end. He's not pacing because he's agitated. He's pacing because he's looking for the source of the stimulus and he can't find it."