“The scale of the trains. HO is 1:87. O is—”

“One to eighty-seven what?”

“It’s a size ratio. HO-scale model trains are one eighty-seventh the size of real trains.”

“Oh…Well, I’m not sure. I know the trains he’s got are small, but I’ll be honest, I was never that good with fractions…What scale are those?” I raised my arm to point; Arlo ducked sideways as if my finger were the tip of a spear, which gave me an opening to move past him. I walked up to the train layout. “Yeah, these look about right…” One train was approaching a bridge near the edge of town; I plucked the locomotive from the track, sending half a dozen passenger cars plunging into a river gorge. “Is this HO size?”

Arlo’s cheeks were billowing in and out, and he’d just about bitten his lower lip off. “Sorry,” I said again. “This is the right size, though, I’m almost sure…Do you have any like this?” Unable to speak, Arlo gestured to a nearby display case—and immediately regretted it.

The display case was locked, but by jiggling the glass doors I managed to knock over a couple of the train cars inside. I turned to Arlo: “Could you open this up for—”

“No.”

“I just want to look at—”

“No.”

“OK.” I shrugged, and jabbed a finger at a random locomotive. “What’s that one called?”

“The Burlington-Northern.”

“And that one?”

“The Union Pacific.”

“And that one?”

“The Illinois Central…Listen, I don’t have time to name every—”

“Ooh! What about that one up there?”

“The Southwest Chief.”

“That one’s pretty slick. Does it come in other colors?”

“No, it doesn’t…Now I’m really kind of busy this morning, so if you aren’t sure what you want—”

“What about monkeys?” I said.

“Wh-what?”

“Monkeys.” I smiled at him. “It’s freakish, I know, but when we were kids my brother was a big-time Curious George fan, and he never totally outgrew it. Do you have any trains with monkeys on them?”

“No. I don’t have anything like that. I’ve never heard of anything like that.”

“What about a case?”

Arlo bit his lip again.

“You know,” I continued, “like a carrying case? Since my brother got into the hobby, he’s made some…interesting new friends. So I thought he might like a case to carry his trains in, when he goes to visit them. You got anything like that, say about this big? In a nice black, maybe?”

A phone began to ring in the store’s back room. Arlo turned his head towards the sound. “You want to get that?” I asked him. It was obvious he did—at least, he wanted to get the hell away from me—but it was just as obvious he was afraid of what might happen to his toys if he left me alone with them. “It’s OK,” I assured him. “I promise I won’t touch anything while you’re gone.”

That really made him nervous—as he headed into the back, he took a last look at the train layout, like he was sure I was going to trash it the minute he was out of sight.

Which, come to think of it, wasn’t a bad idea…

As I stepped back towards the layout, my foot kicked something. It was the magazine Arlo had been reading when I first entered the store: Model Train Enthusiast’s Monthly, something like that. The cover photo showed a sleek locomotive chugging towards a railroad crossing, where—this was weird—a pewter figurine of a boy with a soccer ball had been placed on the tracks, his back to the oncoming train.

The locomotive had a monkey on its side. Not Curious George, or any other friendly cartoon simian—this was a badass nightmare monkey, with sharp fangs tipping a blue-and-red snout. THE MANDRILL, screamed the caption, ON SALE TODAY.

Inset in a box in the lower right-hand corner of the magazine cover was a second, smaller photo, of two women in train-conductor uniforms. The uniforms must have been digitally added, but the doctoring job was so skillful that I almost didn’t notice that the women were me and Annie. The caption on this photo read: “They’re coming for you—details, pg. 23.”

The door to the store’s back room was locked. I kicked it until it wasn’t. The space beyond was lined with more shelves, but instead of trains they held teddy bears, cereal boxes, and toothpaste dispensers…There was a workbench, too, covered with papers and tools, and a couple of empty soccer-ball cartons.

Arlo was gone, of course. I ducked out a side door into the alley. There was no sign of him there, either, but that china doll I’d first seen almost two weeks ago was still sitting in the dumpster, still holding out its hand to shake. Someone had dropped a paper bag over its head.

I broke out my headset: “Hello? Anybody?”

“This is True.”

“Arlo’s on the run,” I told him, hoping this wasn’t news.

“What happened?”

“The short version is, his monkey friends sent him a warning…Please tell me you saw him leave.”

“We’ve had some difficulties with the surveillance.”

“Ah, man…”

“I’m tasking additional resources to the search as we speak; Dexter shouldn’t get far. How long ago did he—”

“Hold on.”

A corkboard had been mounted on the wall above Arlo’s workbench. Looking back at it from the alley door, I noticed that the board didn’t hang quite flush. When I grabbed it by the edge and pulled, it swung outwards. “Holy shit.”

“What?”

“I found the briefcase.”

“You did?”

“Arlo must’ve been in too much of a hurry to take it with him.”

“Perhaps,” True said warily. “But before you open it—”

“Too late.”

There was a brief silence, and I had this clear mental picture of True pursing his lips. “Very well,” he continued. “Describe the contents, without touching them.”

“Right…The case is foam-lined, with slots holding what look like digital stopwatches. Each watch has three small buttons on the left side and one big one on top—don’t worry, I’m not going to push any of them. The brand name on the watch-casings is—”

“Mandrill.”

“Yeah.”

“This next question is very important, Jane. Are any of the stopwatches running right now?”

“Counting down, you mean? No—trust me, that’s the first thing I’d have mentioned. But there is some bad news: Arlo may have left the briefcase behind, but it looks like he took a couple of the watches with him. Two of the slots are empty.”

“All right, I’ll notify the other teams. What I need you to do next is look around the area where you found the case. Can you see anything that might indicate where Dexter is headed?”

“Maybe…” I moved aside a soccer-ball carton. “There’s a map of SFO airport here.”

“Are any of the terminals circled?”

“Yeah, all of them…Listen, True, assuming these watches are what I think they are, is Arlo going to be able to get them through airport security?”

“That’s an irrelevant question.”

“Why?”

“He wants to blow up a crowd, not an airplane. All a security checkpoint will do is save him a few steps.”

Oh, right. “OK then, let’s stop him before he gets there. You want me to go after him on foot, or—”

“No. Stay with the briefcase until Catering secures it.”

“What? Wait a minute, I’m supposed to be hunting Arlo, not—”

“You’ve done your job,” True said. “Stay with the case; another operative will get Dexter.”

“Shit, True…”

He wasn’t listening. I could still hear him on the headset, but he was talking to other people now, ordering a close watch on all bus stops, cab stands, BART stations, even the parking garage where Arlo’s grandmother kept her car. Between that and the general surveillance blanket already covering the neighborhood, Arlo would almost certainly be picked up within a matter of minutes, and there was no way he was getting to the airport. I should have been happy about that, and content to have done my part without any foul-ups, but of course I wasn’t.

I stuck my head out the alley door again, on the off chance that Arlo had doubled back to let me take care of him personally. No such luck. I locked the door, and carried the briefcase into the front of the shop to wait for Catering.