Phocoena's bulkheads are luminous with intelligence. The periscope feed delivers crisp rich realtimes of the maritime nightscape: dark sparkling waves in the foreground, black fingers of dry land reaching into the view from either side. A jumble of bright buildings rises above the coastline in center screen, huddled together against the surrounding darkness. Boxy unlit silhouettes to the south belie the remains of a whole other city south of the Narrows, abandoned in the course of some recent retreat.
The city of Halifax. Or rather, the besieged city-state that Halifax has evidently become.
That naked-eye visual occupies the upper-left quarter of the main panel. Beside it, a false-color interpretation of the same view shows a fuzzy, indistinct cloud enveloping the lit buildings; Clarke thinks of the mantle of a jellyfish, enclosing vital organs. The shroud is largely invisible to human eyes, even rifter ones; to Phocoena's spectrum-spanning senses, it looks like a blue haze of heat lightning. Static-field ionization, Lubin says. A dome of electricity to keep airborne particles at bay.
The seaward frontier is under guard. Not that Clarke ever expected to simply sneak into the harbor and pull up next to the local clam shack; she knew there'd be some kind of security in place. Lubin was expecting mines, so for the last fifty klicks Phocoena crawled towards the coast behind a couple of point drones zig-zagging ahead, luring any countermeasures out of concealment. Those flushed a single burrower lying in wait; awakened by the sound of approaching machinery, it shot from the mud and corkscrewed into the nearest drone with a harmless and anticlimactic clunk.
That lone dud was the only countermeasure they came across on the outer slope. Lubin figures that Halifax's subsurface defenses must have been used up fending off previous incursions. The fact that they haven't been replenished doesn't bode well for the mass-production of industrial goods in the vicinity.
At any rate, against all expectations they've cruised unchallenged all the way here, just outside Halifax Harbor. Only to nearly run into this. Whatever this is.
It's virtually invisible in the sub's lights. It's even less visible to sonar, which can barely pick it up even at point-blank range. A transparent, diaphanous membrane stretches from seabed to surface: the periscope shows a float line holding its upper edge several meters above the waves. It appears to stretch across the entire mouth of the harbor.
It billows inward, as if the Atlantic is leaning on it from the outside. Pinpoint flashes of cold blue light sparkle across its face, sparse ripples of stardust echoing the gentle subsurface surge. Clarke recognizes the effect. It's not the membrane that sparkles, but the tiny bioluminescent creatures colliding with it.
Plankton. It seems somehow encouraging that they still exist, so close to shore.
Lubin's less interested in the light show than its cause. "Must be semipermeable." That would explain the oceanographic impossibility that belied its presence, a sudden sharp halocline rising across their path like a wall. Discrete boundaries are common enough in the sea: brackish water lying atop heavier saline, warm water layered over cold. But the stratification is always horizontal, a parfait of light-over-heavy as inevitable as gravity. A vertical halocline seems to violate the very laws of physics; the membrane itself may have been undetectable to sonar, but the sheer knife-edged discontinuity it produces showed up like a brick wall from a thousand meters away.
"Looks pretty flimsy," Clarke remarks. "Not much to keep us out."
"It's not there for us," Lubin says.
"Well, yeah." It's a ssehemoth filter, obviously. And it must be blocking a whole range of other particles too, to generate this kind of density imbalance. "What I mean is, we can just punch right on through."
"I don't think so," Lubin says.
He brings the periscope down from the surface and sends it sniffing towards the barrier; on the panel, the cowering cityscape disappears in a swirl of bubbles and darkness. Clarke glimpses the 'scope's tether through the viewport, a pale thread of fiberop unwinding overhead. The periscope itself is effectively invisible, a small miracle of dynamic countershading.
Clarke watches it on tactical instead. Lubin brings the drone to within half a meter of the membrane: a faint yellow haze resolves on the right-hand feed, where naked eyes see only darkness. "What's that?" Clarke wonders.
"Bioelectric field," Lubin tells her.
"You mean it's alive?"
"Probably not the membrane itself. I'd guess it's run through with some kind of engineered neurons."
"Really? You sure?"
Lubin shakes his head. "I'm not even sure it's biological—the field strength fits, but it doesn't prove anything." He gives her a look. "Did you think we had a sensor to pick up brain cells at fifty paces?"
No witty rejoinder springs to mind. Clarke turns back to the viewport, and the dim blue aurora flickering beyond. "Like an anorexic smart gel," she murmurs.
"Probably a lot dumber. And a lot more radical—they'd have to tweak the neurons to work at low temperatures, high salinity—the membrane itself could handle osmoregulation, I suppose."
"I don't see any blood vessels. I wonder how they get nutrients."
"Maybe the membrane handles that too. Absorbs them right from seawater."
"What's it for?"
"Other than a filter?" Lubin shrugs. "An alarm, I should think."
"So what do we do?"
Lubin considers a moment. "Poke it," he says.
The periscope lunges forward. On the wide-spectrum display the membrane flares on impact, bright threads radiating from the strike like a fine-veined tracery of yellow lightning. In visible light it just floats there, inert.
"Mmm." Lubin pulls the periscope back. The membrane reverts to lowglow.
"So if it is an alarm," Clarke says, "I'm guessing you've just set it off."
"Not unless Halifax goes to red alert every time a piece of driftwood bumps their perimeter." Lubin runs his finger along a control bar: on tactical, the periscope heads back to the surface. "But I am willing to bet this thing'll scream a lot louder if we actually tear through it. We don't need that kind of attention."
"So what now? Head down the coast a bit, try a land approach?"
Lubin shakes his head. "Underwater was our best shot. A landside approach will be a lot tougher." He grabs a headset off the bulkhead and slips it over his skull. "If we can't get to a hard line, we'll try the local wireless nets. Better than nothing."
He cocoons himself and extends feelers into the attenuate datasphere overhead. Clarke reroutes nav to the copilot's panel and turns Phocoena back into deeper water. An extra klick or so shouldn't interfere with Lubin's trawl, and there's something disquieting about being in such shallow water. It's like looking up to find the roof has crept down while you weren't looking.
Lubin grunts. "Got something."
Clarke taps into Lubin's headset and splits the feed to her own panel. Most of the stream's incomprehensible— numbers and statistics and acronyms, scrolling past too quickly for her to read even if she could make sense of them. Either Lubin's dug beneath the usual user interfaces, or Maelstrom has become so impoverished in the past five years that it can't support advanced graphics any more.
But that can't be. The system has room enough for her own demonic alter-egos, after all. Those are nothing if not graphic.
"So what's it saying?" Clarke asks.
"Missile attack of some kind, down in Maine. They're sending lifters."
She gives up and pulls the 'phones from her eyes.
"That could be our best way in," Lubin muses. "Any vehicles CSIRA deploys will be operating out of a secure site with access to good intel."
"And you think the pilot would be willing to pick up a couple of hitch-hikers in the middle of a contaminated zone?"
Lubin turns his head. Faint lightning flickers around the edges of his eyephones, ephemeral tattoos laid over the scars on his cheeks.
"If there is a pilot," he says, "perhaps he'll be open to persuasion."