"I think we were meant to be next on that list," Creek said. "Acuna was waiting for us in the mall."

"Did you kill him?" Brian asked.

"I don't think so, but I don't think he's in very good shape at the moment. Which reminds me—" Creek fished in his pocket and pulled out Agent Dwight's ID card. "Can you look through the FBI database and see if you can find me anything on an agent named Reginald Dwight?"

"UNE FBI or US FBI?" Brian asked.

"US," Creek said.

"Okay. I was looking for information on Acuna earlier so I should be able to patch back in. Give me a second. I'd guess that's a fake name too, though. For one thing, it's the real name of a twentieth-century composer who went by the name Elton John."

"I don't know him," Creek said.

"Sure you do," Brian said. "Remember that kids' tunes collection I had when I was seven? 'Rocket Man.' I love that tune."

"It was longer ago for some of us than others," Creek said.

"Whatever," Brian said. "Okay, I'm wrong. Turns out there was an FBI agent Reginald Dwight. But I doubt it was your guy, since Agent Dwight was killed three years ago. One of those militia whackjobs in Idaho shot him while the FBI was storming his compound. Whoever your guy is, he's not the walking dead."

"He might be now," Creek said.

"Speaking of which, you look like hell," Brian said. "I'm looking at you through the little camera on your communicator. Your cheek is bleeding. You might want to get that wiped off before one of your trainmates decides you're creepy enough to be checked out by the cops."

"Right," Creek said. "Thanks. I'll call you back soon."

"I'll be here," Brian said, and hung up. Creek lightly brushed his cheek and felt blood moisten his fingers. He wiped them on the inside of his jacket and asked Robin if she had any tissues in her purse. Robin looked up, noticed the blood, nodded, and started digging through her purse. "Shit," she said, after a second.

"What"s wrong?" Creek asked.

"You never realize how much crap you have in your purse until you're looking for one specific thing," Robin said, and started taking objects out of her purse to make her search easier: an address book, a makeup compact, a pen, a tampon applicator. Robin looked up at Creek after the last one. "Pretend you didn't see that," she said.

Creek pointed to the pen. "Can I see that pen?" he asked.

"Sure," Robin said, and handed over the pen.

"This is the one from the store, right?" Creek asked. "The one the gecko man left."

Robin nodded. "Yeah. Why?"

Creek turned the pen around in his hands, and then started taking it apart. After a minute he snapped off the clip and turned it over. "Shit," he said.

"What is it?" Robin asked.

"Bug," Creek said. "They've been tracking us since we left the mall." He dropped the clip and stomped on it with his foot, twisting it into the floor of the train. "We need to get away. Far away."

"Fuck!" Archie pounded the table his computer was on.

This attracted Acuna from the next room. "That better not be what I think it is," he said.

"Creek found the pen," Archie said. "It's not my fault."

"I don't care whose fault it was," Acuna said. "You need to find him, now."

Archie glowered at the screen and from the last coordinates of the pen guessed where Creek and the sheep lady would be in the Metro system. The two of them were approaching L'Enfant Plaza; they were on the Blue Line train but L'Enfant Plaza served every line in the city except the Red and Gray lines. If they got off their train there, who knows where they'd end up.

Got off their train.

"I've got it," Archie said. He closed the track window on the pen and opened up a command line.

"Got what?" Acuna asked.

"My dad was an electrical systems engineer for the DC Metro," Archie said. "Five years ago, the entire electrical system got a refit, and my dad hired me freelance to help with the code. Part of the electrical system deals with managing the power to the trains—"

"Skip the technical shit," Acuna said. "Get to the point. Quick."

"The Metro trains are maglev—magnetic levitation," Archie said. "Each train used to get full power for its magnets no matter what, but that got too expensive. The retrofit allowed each train to use only as much power as it needs to run, based on the gross weight of the train. The amount of power allotted to each train adjusts in real time."

"So?" Acuna said.

"So, every time someone gets on a train or off a train, the amount of power sent to the train increases or decreases by an amount that's in a direct relationship to the weight of those people." Archie looked over to Acuna, whose face was a dangerous shade of blank. He decided to make it even simpler. "If we can guess how much the two of them weigh, we might be able to guess if they've gotten off their train and where they might be going."

Acuna's eyebrows shot up; he got it. "You'll need to get into the Metro's system," he said.

Archie had turned back to his computer. "Dad had a back door into the system he let me use while I was freelancing," he said. "I'm guessing after he retired no one bothered to close it."

Fifteen seconds later "Nope, they didn't. We're in," Archie said. "You saw the two of them, right? How much would you guess they weighed?"

"I don't know," Acuna said. "Both of them seemed pretty fit."

"How tall were they?" Archie asked.

"He was about my height," Acuna said. "I'm about five ten. She was a few inches shorter, I'd guess."

"About five six, then, let's say," Archie said. "So let's say he's about 180 and she's 120, so that's 300 pounds, which is about 136 kilos." Archie punched up a calculator on his computer screen and pounded in some numbers, and then pointed at the resulting number. "All right, if the train they got in was empty, that's how much energy would need to be fed to the train to compensate for their additional weight when they got on. So we're looking for something in that neighborhood."

Archie opened up another window. "Okay, here's a list of the Blue Line trains currently in operation. Click this here, and now we have them arranged by when they stopped at the Arlington Mall station. Disregard the trains going out from DC, we have four trains that stopped at the station in the time window we're looking for." Archie selected each of the trains; four new windows opened up. Archie selected the "Power Management" option for each; each window became a spiky chart.

"No," Archie said, closing one chart. "No," he said again a few seconds later, closing the next chart. "Yes!" he said to the third one, and blew up the chart to maximum size. "Look here," Archie said, pointing to the graph. "Power goes down because people are stepping off the train, then you get some noise because people are stepping off and on simultaneously. But here"—Archie pointed to a small uptick—"is a power boost that's right near what we're looking for, for about 136 kilos. That's assuming they stepped on the train together, as opposed to one fatso."

"That's swell," Acuna said, and Archie realized that of the many things Acuna might be, "patient" was never going to be one of them. "Now tell me if they're still on the goddamn train."

Archie pulled up a real-time chart of the train's power management, which showed the train's last five minutes of power usage. "Looks like the train just left L'Enfant," Archie said. "Lots of people getting on and off the train, but none looks like the 136-kilo power spike or drop. I'm guessing they're still on the train."

"You're guessing," Acuna said.

"Mr. Acuna," Archie said. "I'm doing the best I can. I can't help that he busted the tracking pen. But short of the tracking pen or getting a feed from the Metro cameras, this is as good as it gets."