PLEASE REMAIN WHERE YOU ARE, MS. PLEIADES, said an override message. AN ATTENDANT WILL ARRIVE AT YOUR POSITION SHORTLY IN ORDER TO HELP YOU RETURN TO YOUR SEAT FOR LANDING.

  “Double great.”

  Ahead, beyond the curve of the dirigible’s skin, she spotted the massive, squat bulk of the Pentagon, bristling with missiles, antennae and other security measures... still a highly-protected enclave, even ten years after the Department of Defense moved its headquarters to “an undisclosed location in Texas.”

  Soon, the mooring towers and docking ports of Reagan-Clinton National Skydrome would appear, signalling the end of her cross-continental voyage. And of any chance for a blemish-free start to her new career in Big Time Media.

  “I don’t suppose any of you have bright ideas?” She addressed the group mind.

  But it had already started to unravel. Membership numbers were falling fast, like rats deserting a sinking ship, Or—more accurately—monkeys. Moving on to the next shiny thing.

  Sorry, Tor. People are distracted. They’ve been dropping out to watch the opening of the Artifact Conference. You may even glimpse some limos arriving at the Naval Research Center, just across the Potomac. Take a look as the Spirit starts turning for final approach...

  Blasted fickle amateurs! Tor had made good use of smart mobs on several occasions. But this time was likely to prove an embarrassment. None of them would have to pay fines or face disapproval in a new job.

  Still, a few of us remain worried, the voice continued.

  That rumor had something about it.

  I can’t put my finger on it.

  The “voice” was starting to sound individualized and had even used the first person “I”. And yet, Tor drew some strength from the support. Before an attendant arrived to escort her below, there was still time for a little last minute tenacity.

  “Can I assume we still have some zep aficionados in attendance?”

  Hardly anyone else, Tor.

  Some us are fanatics.

  “Good, then let’s apply fanatical expertise. Think about that leakage we discussed a while ago. We’ve been assuming that this zeppelin is making hydrogen to make up for a major seep. Have any of those amateur scientists studied the air near Spirit’s flight path?”

  A pause.

  Yes, several have reported. They found no dangerous levels of hydrogen in the vicinity of the ship, or in its wake. The seep is probably dissipating so fast....

  “Please clarify. No dangerous levels? Is it possible they found no sign of a hydrogen leak at all?”

  The pause extended several seconds longer, this time. Suddenly the number of participants in the group stopped falling. In the corner of Tor’s TruVu, she saw membership levels start to rise again.

  Now that’s interesting, throbbed the voice in her jaw.

  Several of those Am ateur Scientists have joined us now.

  They report seeing no appreciable leakage. Zero extra hydrogen along the flight path. How did you know?

  “I didn’t. Call it a hunch.”

  But at the rate that Spirit has been replacing hydrogen...

  “There has to be some kind of leak. Right. It must be going somewhere.”

  Tor frowned. She could see a shadow moving beyond the grove of tall, cylindrical gas-cells. A figure approaching. A crewman or attendant, coming to take her, firmly, gently, insistently, back to her seat. The shape wavered and warped as seen through the mostly transparent polymer tubes—slightly pinkish for hydrogen and then greenish-tinted for helium.

  Tor blinked. Suddenly feeling so dry-mouthed that she could not speak aloud, only sub-vocalize.

  “Ask the AmScis to take more spectral scans along the path of this zeppelin. Only this time look for helium.”

  The inner surfaces of her TruVus showed a flurry of indicators. Amateur scientific instruments, computer-controlled from private backyards or rooftops, could zoom quickly toward any patch of sky. There were thousands of such pocket observatories, in and around any urban center—hobbyists with access to better instrumentation than the previous generation could imagine. Dotted lines appeared. Each showed the viewing angle of some home-taught astronomer, ecologist or meteorologist, turning a hand- or kit-made instrument toward the majestic cigar shape of the Spirit of Chula Vista...

  ...which had passed Arlington and Pentagon City, following its faithful tug into a final tracked loop, approaching the dedicated zeppelin port that served Washington DC.

  Yes, Tor. There is helium.

  Quite a lot of it, in fact.

  A plume that stretches at least a hundred klicks behind the Spirit. Nobody notice before this, because helium is inert and utterly safe, so no environmental monitors were tuned to look for it.

  The voice was grim. Much less individualized. With ad hoc membership levels suddenly skyrocketing, summaries and updates must be spewing at incredible pace.

  Your suspicion appears to be well-based.

  Extrapolating the rate of helium loss backward in time, half of that gas may have been lost by now....

  “...replaced in these green cells by another gas.”

  Tor nodded. “I think we’ve found the missing hydrogen, people.”

  It all made sense, now. Smart polymers were programmable—all the way down to the permeability of any patch of these gas-containing cells. If you did it very cleverly, you might insert a timed instruction where two gas cells touched, commanding one cell to leak into another. Create a daisy chain. Vent helium into the sky. Transfer gas from hydrogen cells into the helium cells to maintain pressure, so that non one notices. Trigger automatic systems to crack onboard water and “replace” the hydrogen, replenishing the main cells. Allow the company to assume a slow leak into the sky is responsible. Continue.

  Continue until you have replaced the helium in enough of the green cells to turn the Spirit into a flying bomb.

  “The process must be almost complete by now,” she murmured, peering ahead toward the great zep-port, where dozens of mighty dirigibles could already be seen, some of them vastly larger than this passenger liner, bobbing gently at their moorings. Spindly fly-cranes went swooping back and forth as they plucked shipping containers from ocean freighters at the nearby Potomac Docks, gracefully transferring the air-gel crates to waiting cargo-zeppelins for the journey across land. A deceptively graceful, swaying dance that propelled the engines of commerce.

  The passenger terminal—dwarfed by comparison to those giants—seemed to beckon with a promise of safety. But indicators showed that it still lay as much as ten minutes away.

  We have issued a clamor,Tor, assured the voice in her jaw. Every channel. Every agency.

  A glance at telltales showed Tor that, indeed, the group mind was doing its best. Shouting alarm toward every official protective service, from Defense to Homeworld Security. Individual members were lapel-grabbing friends and acquaintances while smart mob attendance levels climbed into five figures, and more. At this rate, surely the professionals would be taking heed. Any minute now.

  “Too slow,” she said, watching the figures with a sinking heart. With each second that it took to get action from the Protector Caste, the perpetrators of this scheme would also grow aware that the jig is up. Their plan was discovered. And they would have a speedup option.

  Speaking of the perps, Tor wondered aloud.

  “What can they be hoping to accomplish?”

  We’re pondering that, Tor. Timing suggests that they aim to disrupt the Artifact Conference. Delegates arriving at the Naval Research Center are having a cocktail reception on the embankment right now, offering a fine view toward the zep port, across the river.

  Of course it is possible that the reffers plan to do more than just put on a show, while murdering three hundred passengers. We are checking to see if the Umberto tug has been meddled-with. Perhaps the plan is to hop rails and collide with a large cargo zep, before detonation. Such a fireball might be seen all the way from the Capitol, and disrupt the port for months

  One problem with a smart mob. The very same traits that multiplied intelligence could also make it seem dispassionate. Insensitive. Individual members surely felt anguish and concern over Tor’s plight. She might even access their messages, if she had time for commiseration.

  But pragmatic help was preferable. She kept to the group mind level.

  One (anonymous) member (a whistle-blower?) has suggested a bizarre plan using a flying-crane at the zep port to grab the Spirit of Chula Vista when it passes near. The crane would then hurl the Spirit across the river, to explode right at the Naval Research Center! In theory, it might just barely be possible to incinerate —

  “Enough!” Tor cut in. Almost a minute had passed since realization of danger and the issuance of a clamor. And so far, nobody had offered anything like a practical suggestion.

  “Don’t forget that I’m here, now. We have to do something.”

  Yes, the voice replied, eagerly and without the usual hesitation. There is sufficient probable cause to get a posse writ. Especially with your credibility scores. We can act, with you performing the hands-on role.

  Operational ideas follow:

  CUT THE TOWING CABLE. (Emergency release is in the gondola. Reachable in four minutes. Risk factor: possible interference from staff. Ineffective at saving the zeppelin/passengers.)

  PERSUADE ZEP COMPANY TO COMMENCE EMERGENCY VENTING PROCEDURES. (Communication in progress. Response so far: obstinate refusal...)

  PERSUADE ONBOARD STAFF TO COMMENCE EMERGENCY VENTING PROCEDURES. (Attempting communication despite company interference...)

  PERSUADE COMPANY TO ORDER PASSENGER EVACUATION. (Communication in progress. Response so far: obstinate refusal...)

  UPGRADE CLAMOR. INDEPENDENTLY CONTACT PASSENGERS URGING THEM TO EVACUATE. (Dangers: delay, disbelief, panic, injuries, fatalities, lawsuits....)

  The list of suggestions seemed to scroll on and on. Rank-ordered by plausibility-evaluation algorithms, slanted by urgency, and scored by likelihood of successful outcome. Individuals and sub-groups within the smart mob split apart to urge different options with frantic vehemence. The inner face of her TruVu flared, threatening overload.

  “Oh, screw this,” Tor muttered, reaching up and tearing off the specs.

  The real world—unfiltered. For all of its paucity of layering and data-supported detail, it had one special trait.

  It’s where I am about to die.

  Unless I do something fast.

  At that moment, the zep-crew attendant arrived. He rounded the final corner of a towering gas cell, coming into direct view—no longer a shadowy authority figure, warped and refracted by the tinted polymer membranes. Up close, it turned out to be a small man, middle-aged and clearly frightened by what his own TruVus had started telling him. All intention to arrest or detain Tor had already evaporated during the last minute. She could see this in his face, as clearly as if she had been monitoring vital signs.

  WARREN, said a company name tag.

  “Wha — what can I do to help?” he asked in a hoarse whisper.

  Though hired for gracile weight and people skills, the fellow clearly possessed some courage. By now he knew what filled many of the slim, green-tinted membranes surrounding them both. And it didn’t take a genius to realize the zep company was unlikely to be helpful during the time they had left.

  “Tool kit!” Tor held out her hand.

  Warren fumbled at his waist pouch. Precious seconds passed as he unfolded a slim implement case. Tor found one promising item—a vibrocutter.

  “Keyed to your biometrics?”

  He nodded. Passengers weren’t allowed to bring anything aboard that might become a weapon. This cutter would respond to his personal touch and no other. It required not only a fingerprint, but volition—physiological signs of the owner’s will.

  “You must do the cutting, then.”

  “C-cutting...?”

  Tor explained quickly.

  “We’ve got to vent this ship. Empty the gas upward. That’ll happen to a main cell if it is ruptured anywhere along its length, right? Automatically?”

  A shaky nod. She could tell Warren was getting online advice, perhaps from the Zep Company. More likely from the same smart mob that she had called into being. She felt strong temptation to put her own specs back on—to link-in once more. But she resisted. Kibbitzers would only slow her down right now.

  “It might work...” said the attendant in a frightened whisper. “But the reffers will realize, as soon as we start —”

  “They realize now!” She tried not to shout. “We may have only moments to act.”

  Another nod. This time a bit stronger, though Warren was shaking so badly that Tor had to help him draw the cutter from its sleeve. She steadied his hand.

  “We must slice through a helium bag in order to reach the big hydro cell,” he said, pressing the biometric-sensitive stud. Reacting to his individual touch, a knife edge of acoustic waves began to flicker at the cutter tip, sharper than steel. A soft tone filled the air.

  Tor swallowed hard. That flicker resembled a hot flame.

  “Pick one.”

  They had no way to tell which of the greenish helium cells had been refilled, or what would happen when the cutter helped unite gas from neighboring compartments. Perhaps the only thing accomplished would be an early detonation. But even that had advantages, if it messed up the timing of this scheme.

  One lesson you learned early nowadays: any citizen can wind up being a front-line soldier for civilization, at any time.

  In other words, expendable.

  “That one.” Warren moved toward the nearest.

  Though she had doffed her TruVu specs, there was still a link. The smart mob’s Voice retained access to the conduction channel in her jaw.

  Tor, said the group mind. We’re getting feed through Warren’s goggles. Are you listening? There is a third possibility. in addition to helium and hydrogen. Some of the cells may have been packed with —

  She bit down twice on her left canine tooth, cutting off the distraction in order to monitor her omni-sniffer. She inhaled deeply, with her eye on the indicator as Warren made a gliding, slicing motion with his cutter.

  The greenish envelope opened, as if along a seam. Edges rippled apart as invisible gas—appreciably cooler—swept over them both.

  HELIUM said the readout. Tor sighed relief.

  “This one’s not poisonous.”

  Warren nodded. “But no oxygen. You can smother.” He ducked his head aside and took another deep breath. The next words had a squeaky, high-pitched quality. “Gotta move fast.”

  Through the vent he slipped, hurrying quickly to the other side of the green cell, where it touched one of the great chambers of hydrogen.

  Warren made a rapid slash.

  Klaxons bellowed, responding to the damage automatically. (Or else, had the company chosen that moment, after several criminally-negligent minutes, to finally admit the inevitable?) A voice boomed insistently, ordering passengers to move—calmly and carefully—to their escape stations.

  That same instant, the giant hydrogen gas cell convulsed, twitching like a giant bowel caught in a spasm. The entire pinkish tube—bigger than a jumbo jet—contracted, starting at the bottom and squeezing toward a sudden opening at the very top, spewing its contents skyward.

  Backwash hurled Warren across the green tube. Tor managed to grab his collar, dragging him out to the walkway. There seemed to be nothing satisfying about the ‘air’ that she sucked into her lungs, and she started seeing spots before her eyes. The little man was in worse shape, gasping wildly in high-pitched squeaks.

  Somehow, Tor hauled him a dozen meters along the gangway, barely escaping descending folds of the deflated cell, arriving at last where breathing felt better. Did we make any difference? She wondered, wildly.

  Instinctively, Tor slipped back on her TruVu specs. Immersed again in the info-maelstrom, it took moments to focus.

  One image showed gouts of flame pouring from a hole in the roof of a majestic sky-ship. Another revealed the zeppelin’s nose starting to slant steeply as the tug-locomotive pulled frantically on its tow cable, reeling the behemoth toward the ground. Spirit resisted, like a stallion, bucking and clinging to altitude.

  Tor briefly quailed. Oh Lord, what have we done?

  A thought suddenly occurred to Tor. She and Warren had done this entirely based on information that had come to them from outside. From a group mind of zeppelin aficionados and amateur scientists who claimed that a lot of extra hydrogen had to be going somewhere, and it must be stored in some of the former helium cells. But that helium cell had been okay.

  And now, amid all the commotion, she wondered. What about the smart mob? Could that group be a front for clever reffers, who were using her to do their dirty work? Feeding false information, in order to get precisely this effect?

  The doubt passed through her mind in seconds. And back out again. This smart mob was open and public. If something smelled about it, another mob would have formed by now, clamoring like mad and exposing the lies. Anyway, if no helium cells had been tampered with, the worst that she and Warren could do was bring a temporarily disabled Spirit of Chula Vista down to a bumpy but safe landing atop its tug.

  Newsworthy. But not very. And that realization firmed her resolve.

  Tor yanked the attendant onto his feet and urged him to move uphill, toward the stern, along a narrow path that now inclined the other way. “Come on!” She called to Warren, her voice still squeaky from helium. “We’ve got to do more!”

  Warren tried gamely. But she had to steady him as the path gradually steepened. When he prepared to slash at another green cell, farther aft, Tor braced his elbow.

  Before he struck, through the omniscient gaze of her TruVu, Tor abruptly saw three more holes appear in the zep’s broad roof, spewing clouds of gas, transparent but highly-refracting, resembling billowy ripples in space.

  Was the zep company finally taking action? Had the reffers made their move? Or had the first expulsion triggered some kind of compensating release from automatic valves, elsewhere on the ship?

  As if pondering the same questions, the Voice in her jaw mused.