"What do the cops know?"
"They know nothing." Rich suddenly looked serious.
"Okay." Judith steered him towards what looked to be the control vehicle. "Tell me why we're here, then."
"Team Green rescanned the area with the new gamma spectroscope they just got hold of from Lockheed. The idea was to calibrate it against our old readings, but what they found-they thought it was an instrument error at first. Turns out that MBTA's civil engineers recently removed the false walls at the ends of the Blue Line platforms so they could run longer trains. That's when we began getting the emission spectra. More sensitive detectors, less concrete and junk in the way-that's how it works. There's an older platform behind the false walls, and it looks like there's something down there."
Down? "How far down?" she asked.
"Below the surface? Not far. This lot is all built up on reclaimed land-if that's what you're thinking."
She nodded. "Suppose it's not deep at all, in fairyland. Suppose it's on the surface. They could just waltz in and plant a bomb. Nobody would notice?"
"It's not that simple," said Dr. Rand, taking her by surprise. "Let's get you a hard hat and jacket and head down to the site."
"You've already opened it up?" she demanded.
"Not yet, we were waiting for you." He grinned unnerv-ingly. "Step this way."
All railway stations-like all public buildings-have two faces. One face, the one Herz was familiar with, was the one that welcomed commuters every day: down the stairs into the MBTA station, through the ticket hall and the steps or ramps down to the platforms where the Blue Line trains and Green Line streetcars thundered and squealed. The other face was the one familiar to the MBTA workers who kept the system running. Narrow corridors and cramped offices up top, anonymous doors leading into dusty, ill-lit engineering spaces down below, and then the tracksidc access, past warning signs and notices informing the public that they endangered both their lives and their wallets if they ventured past them. "Follow me, sir, ma'am," said the MBTA transit cop Rand was using as an escort. "It's this way."
From one end of a deserted Blue Line platform-its entrance sealed off by police tape, the passengers diverted to a different part of the station-he led them down a short ramp onto the trackside. Herz glanced up. The roof of the tunnel was concrete, but it was also flat, a giveaway sign of cut and cover construction: there couldn't be much soil up there. Then she focused on following the officer as he led them alongside the tracks and then through an archway to the side.
"Wow." Judith glanced around in the gloom. "This is it?" Someone had strung a bunch of outdoor inspection lamps along the sixty-foot stretch of platform that started at shoulder height beside her. It was almost ankle-deep in dirt, the walls filthy.
"No, it's down here," said Lucius, pointing.
She followed his finger down, and realized with a start that the platform wasn't solid-it was built up on piles. The darkness below seemed almost palpable. She bent down, pulling her own flashlight out. "Where am I supposed to be looking?" she asked. "And has anyone been under here yet?"
"One moment," said Rand. "Officer, would you mind going back up for the rest of my team? Tell Mary Wang that I want her to bring the spectroscope with her."
Herz half-expected the cop to object to leaving two civilians down here on their own, but evidently someone had got to him: he mumbled an acknowledgment and set off immediately, leaving them alone.
"No, nobody's been under there yet," said Rand. "That's why you're here. You mentioned that the person behind this incident had some disturbing habits involving trip wires, didn't you? We're going to take this very slowly."
"Good," said Herz, suppressing an involuntary shudder.
The next half hour passed slowly, as half a dozen members of Rand's team made their way down to the platform with boxes of equipment in hand. Wang arrived first, wheeling a metal flight case trailing a length of electrical cable behind. She was petite, so short that the case nearly reached her shoulders. "Let's see where it is," she said encouragingly, then proceeded to shepherd the case along the platform at a snail's pace, pausing every meter or so to take readings, which she marked on the platform using a spray can.
"Where do you make it?" Rand asked her.
"I think it's under there." She pointed to a spot about two thirds of the way down the platform, near the rear wall. "I just want to double-check the emission strength and recalibrate against the reference sample."
Rand glanced at Herz and pulled a face. "Granite," he said. "Plays hell with our instruments because it's naturally radioactive."
"But Boston isn't built on-"
"No, but where did the gravel in the aggregate under the platform come from? Or the dye on those tiles?" His gesture took in the soot-smudged rear wall. "Or the stones in the track ballast?"
"But granite-"
"It's not the only problem we've got," Rand continued, in tones of relish that suggested he was missing the classroom: "Would you believe, bananas? Lots of potassium in bananas. You put a bunch of bananas next to a gamma source and a scattering spectrometer on the other side and they can fool you into thinking you're staring at a shipping container full of yellowcake. So we've got to go carefully." Wang and a couple of assistants were hauling her balky boxful of sensors over the platform again, peering at the instrument panel on top with the aid of a head-mounted flashlight.
"It's here!" she called, pointing straight down. "Whatever it is," she added conversationally, "but it sure looks like a pit to me. Lots of HEU in there. Could have come right out of one of our own storage facilities, it's so sharp."
"Nice work." Rand eased himself down at the side of the platform and lowered himself to the track bed. He looked up at Herz. "Want to come and see for yourself? Hey, Jack, get yourself over here!"
Judith jumped down to the track bed beside him. Her hands felt clammy. Is this it? she asked herself. The sense of momentous events, of living through history, ran damp fingertips up and down her spine. "Watch out," she warned.
"No problem, ma'am." Rand's associate, Jack, had an indefinite air about him that made her think, Marine Corps: but not the dumb stereotype kind. "Let's start by looking for lights."
Another half hour crept by as Jack-and another three specialists, experts in bomb disposal and booby traps- checked from a distance to ensure there were no surprises. "There arc no wires, sir," Jack finally reported to Dr. Rand. "No IR beams either, far as I can tell. Just a large trunk over against the wall, right where Mary said."
The hair on Judith's neck rose. It's real, she admitted to herself. "Okay, let's take a closer look," said Rand. And without further ado, he dropped down onto hands and knees and shuffled under the platform. Herz blinked for a moment, then followed his example. At least I won't have to worry about the dry-cleaning bill if Jack's wrong, part of her mind whispered.
Jack had set up a couple of lanterns around the trunk. Close up, down between the pillars supporting the platform, it didn't look like much. But Rand seemed entranced. "That's our puppy all right!" He sounded as enthusiastic as a plane spotter who'd managed to photograph the latest black silhouette out at Groom Lake.
"What exactly is it?" Herz. asked warily.
"Looks like an FADM to me. An enhanced storage version of the old SSADM, based on the W54 pit. Don't know what it's doing here, but someone is going to catch
it in the neck over this. See that combination lock there?" He pointed. "It's closed. And, wait..." He fell silent for a few seconds. "Got it. Did you see that red flash? That's the arming indicator. It blinks once a minute while the device is live. This one's live. There's a trembler mechanism and a tamper alarm inside the casing. Try to move it or crack it open and the detonation master controller will dump the core safety ballast and go to detonate immediately." He fell silent again.