I backed out of the car and jerked open the driver’s door. Dumbly, I picked up the thermos and stuck it in the pocket of my peacoat. How had Morrell’s thermos ended up in Billy’s car? Maybe Billy had one like it, and the i in the Ti logo was prone to chipping, not that I could picture Billy or Josie drinking, especially not bourbon.

Morrell had been with me on Saturday when Buffalo Bill thumped in, demanding his grandson, but even if Morrell were the kind of guy who would go looking for Billy without telling me, he wasn’t physically up to the job. And he wasn’t much of a drinker.

I opened my phone and pressed the speed-dial key for Morrell, then shut the cover again: it was past two-thirty. I didn’t need to wake him up for something I could ask him in the morning. Anyway, I had the two thugs who’d pried open the trunk. They could answer a few questions.

As if on cue, a commotion erupted behind me: Mr. Contreras shouted, Mitch barked full throttle, and then I heard gravel spitting as our captives started running. I backed out of the bracken as fast as I could, dropping the two books in my haste. The youths were running headlong up Ewing. Mitch broke free of Mr. Contreras and tore after them.

I screamed at Mitch to come, but he didn’t even break his stride. I pelted after him. I heard Mr. Contreras’s lumbering tread for a few yards, but the traffic overhead soon swallowed the sound. At 100th Street, the youths turned west, toward the river, Mitch hot on their heels. I’d gone a block before admitting I’d lost them. I stood still, trying to hear where they’d gone, but couldn’t make out anything except the thunking of trucks on the Skyway and the lapping of the river somewhere on my left.

I turned back to Ewing. If Mitch caught them, I’d hear the uproar. But I would be in way over my head if I left the main road and tried to thread my way on foot through the dead-end streets and marshy lots that these guys called home.

Behind me, a set of headlights picked me out like a deer on a country road. I ducked behind a Dumpster. The car stopped. I huddled in the dark for a moment until I realized it was my own car, that Mr. Contreras, with more sense than I possessed right now, had brought it up from where I’d abandoned it.

“Where are you, doll?” The old man had climbed out of the driver’s seat and was scanning the empty street. “I seen you a minute ago. Oh-where’s Mitch? I’m sorry, he just suddenly jumped and took after them punks. They go down the road there?”

“Yeah. But they could be anywhere by now, including the middle of the swamp.”

“I’m so sorry, doll, I see why you don’t want me butting in when you’re working, can’t even hold on to the damn dog.” He hung his head.

“Easy, easy.” I patted his arm. “Mitch is strong, and he wanted those guys. If I hadn’t been playing Annie Oakley back there, maybe Mitch wouldn’t have gotten so wound up to begin with. And if I’d taken the car, instead of thinking I could catch two twenty-year-olds on foot-” I bit off the words: second-guessing and guilt-tripping are luxuries a good detective should never indulge in.

My neighbor and I called to the dog for a minute or two, straining to hear him. The Skyway is a diagonal road and was to our left here, close enough that the traffic made it hard to hear other sounds.

“This isn’t doing any good,” I said abruptly. “We’ll drive the area. If we don’t see him soon, let’s come back in daylight with Peppy-she might nose him out.”

Mr. Contreras agreed, at least with the first part of my suggestion. When he’d climbed into the passenger seat, he said, “You go on home, get some shut-eye, and bring Peppy back, but I ain’t gonna leave Mitch out here. He never spent the night outside by himself before, and I’m not gonna have him start now.”

I didn’t try to argue with him-I sort of felt the same way myself. We crawled west on 100th Street, Mr. Contreras with his head out the window, giving an ear-piercing whistle every few yards. As we got close to the river, the ram-shackle houses gave way to collapsing warehouses and sheds. The two punks could have sought refuge in any of them. Mitch might be lying there-I clipped the thought off.

We made a painstaking circuit of the four blocks that lie between the Skyway and the river. Only once did we pass another car, a one-eyed bandit missing the right headlight. The driver was a skinny, nervous kid who ducked his head when he saw us.

At the river, I got out of the car. I keep a real flashlight, industrial-strength, in my glove compartment. While Mr. Contreras stood behind me and played the light along the bank, I poked around in the dead marsh grasses.

We were lucky that we were on the far edge of fall, when the ranker vegetation has frozen and dissolved, and the marsh grasses no longer provide cover to a million biting insects. Even so, the ground was a clammy mud that sucked at my shoes; I felt the cold brackish water oozing into them.

I heard slithering and rustling in the underbrush and came to a standstill. “Mitch,” I called softly.

The rustling stopped briefly, then started again. A kind of rat came out, followed by a little family, and slid into the river. I moved on.

I passed a man lying in the grasses, so still I thought he might be dead. My skin curling with disgust, I went close enough to hear him breathe, a slow, kerchunky sound. Mr. Contreras followed me with the flashlight, and I saw the telltale needle lying across the open lid of a beer can. I left him to such dreams as remained for him and climbed back up the embankment to the bridge.

We crossed the river in a strained silence and tried to repeat the maneuver on the far side, both of us calling to Mitch. It was after five, with the eastern sky turning that lighter shade of gray that presages the dying year’s dawn, when we staggered back to the car and collapsed against the seats.

I pulled out my city maps. The marshland was huge on the West Side; a team of trained searchers, with dogs, could spend a week here without covering half of it. Beyond the expanse of marsh, the network of streets started up again, mile upon mile of abandoned houses and junkyards where a dog might be lying. I didn’t really believe our two thugs would have gone west of the river: people stay close to the space they know. These guys had found or hijacked or whatever they’d done to the Miata close to their home base.

“I don’t know what we do next,” I said dully.

My feet were numb from the cold and damp, my eyelids ached with fatigue. Mr. Contreras is eighty-one; I didn’t know how he was staying upright.

“Me neither, cookie, me neither. I just should never’ve-” He broke off his lamentation before I did. “Do you see that?”

He pointed down the road at a dark shape. “Probably just a deer or something, but put on the headlights, doll, put on the headlights.”

I put on the headlights and got out to crouch in the road. “Mitch? Mitch? Come here, boy, come here!”

He was caked in mud, his tongue lolling with exhaustion and thirst. When he saw me, he gave a little “whoof” of relief and started licking my face. Mr. Contreras tumbled out of the car and was hugging the dog, calling him names, telling him how he’d skin him alive if he ever pulled a stunt like that again.

A car came up behind us and blared on its horn. The three of us jumped: we’d had the road to ourselves for so long we’d forgotten it was a thoroughfare. Mitch’s thick leather leash was still attached to his collar. I tried to drag him back to the car, but he planted his feet and growled.

“What is it, boy? Huh? You got something in your feet?” I felt his paws, but, although the pads were nicked in places, I couldn’t find anything lodged in them.

He stood up and picked up something from the road and dropped it at my feet. He turned to look back down the road, back west, the way he’d come from, picked up the thing and dropped it again.