“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 are 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.
“Does ‘detonate immediately’ mean what I think it means?” asked Herz. It’s been here for months, it’s not going to go off right away, she told herself, trying to keep a lid on her fear.
“Yes, it probably does.” Dr. Rand sounded distracted. “Hmm, this is an interesting one. I need to think about it for a while.”
You need to—Herz wrenched herself back on track. “What happens now?” she asked.
“Let’s go up top,” suggested Rand.
“Okay.” They scrambled backwards until they reached the track bed, and could stand up. “Well?” she asked.
“I got its serial number,” Rand said happily. “Now we can cross-check against the inventory and see where it came from. If it’s on the books, and if we can trust the books, then we can just requisition the PAL combination and open it up, at which point there’s a big red OFF switch, sort of.” A shadow crossed his face: “Of course, if it’s a ghost device, like the big lump of instant sunshine you stumbled across in Cambridge, we might be in trouble.”
“What kind of trouble? Tell me everything. I’ve got to tell the colonel.”
“Well…” Rand glanced from side to side, ensuring nobody else was within earshot. “If it’s just a pony nuke that’s been stolen from our own inventory, then we can switch it off, no problem. Then we get medieval on whoever let it go walkabout. But you remember the big one? That wasn’t in our inventory, although it came off the same production line. If this is the same, well, I hope it isn’t, because that would mean hostiles have penetrated our current warhead production line, and that’s not supposed to be possible. And we won’t have the permissive action lock keys to deactivate it. So the best we can hope for is a controlled explosion.”
“A controlled—” Herz couldn’t help herself: her voice rose to an outraged squeal—“explosion?”
“Please, calm down! It’s not as bad as it sounds. We know the geometry of the device, where the components sit in the casing. These small nukes are actually very delicate—if the explosive lens array around the pit goes off even a microsecond or two out of sequence, it won’t implode properly. No implosion, no nuclear reaction. So what happens is, we position an array of high-speed shaped charges around it and blow holes in the implosion assembly. Worst case, we get a fizzle—it squirts out white-hot molten uranium shrapnel from each end, and a burst of neutrons. But no supercriticality, no mushroom cloud in downtown Boston. We’ve got time to plan how to deal with it, so before we do that we pour about a hundred tons of barium-enriched concrete around it and hollow out a blast pit under the gadget to contain the fragments.” He grinned. “But these gadgets don’t grow on trees. I’m betting that your mysterious extradimensional freaks stole it from our inventory. In which case, all I need to do is make a phone call to the right people, and they give me a number, and—” he snapped his fingers “—it’s a wrap.”
“But you forgot one thing,” Judith said slowly.
“Oh, yes?” Rand looked interested.