"The what ware?"

Auger interrupted. "She means the guidance system will stop working without any warning."

"Can I start it again?"

"Yes," Skellsgard said. "You'll need to implement an immediate reboot. That's the easy bit-Auger can

show you how to do that. The difficult bit is that you'll need to get the ship back on course before you sc.r.a.pe the sides of the tunnel."

"Sc.r.a.ping sounds painful. And what kind of angle exceeds seven hundred and twenty degrees, anyway?"

"The kind you'll get a headache thinking about, so don't."

Floyd moved the joystick again, getting the feel of it. "How long will I have to get us back on track before we sc.r.a.pe?"

"Depends. Ten, maybe fifteen seconds. That should be enough time for you to override and correct your trajectory. There'll be an audible alarm when the guidance system crashes, telling you you're about to become an interesting smear on the inside of the tunnel."

"Anything else I need to know?"

"Only about a lifetime's worth, but that's the way it is. Just keep an eye on the grid and try to antic.i.p.ate the drift gradients before they sneak up on you. You should see bunching of the grid lines. The ship's

response time is slow, so make sure you keep your control inputs small and discrete, giving the ship time to answer the helm before you make another correction."

"Now you're talking a language I almost understand."

"Have you ever flown transatmospherics?"

"I don't think so," Floyd said.

"He used to be a trawlerman," Auger said. "Before that I think he drove barges of some kind. They're a

kind of boat," she added.

"Did those barges turn on a dime?" Skellsgard said.

"No," Floyd said. "Matter of fact, they took about a nautical mile to slow down. And you had to

antic.i.p.ate every bend in the river long before you saw it."

"Or else you'd sc.r.a.pe the banks," Skellsgard said, nodding approvingly. "Well, all you need to do is

think of this ship as a big old barge with some unusual characteristics, and the tunnel walls as banks you really, really don't want to sc.r.a.pe. Can you get your head around that?"

"I can try," Floyd said.

"Then maybe you can bring this baby home in one piece after all."

Floyd shrugged, letting the joystick return to its central position. Skellsgard was making a big effort to

sound optimistic, but her cheerfulness was paper-thin. "Say," he began, "if you're talking to us now, why can't you talk us all the way home? You know, the way the guys in the tower talk down planes in the movies when the pilot's had a heart attack and some poor Joe is at the controls?"

"We lose this link as soon as we shoot a ship into the tunnel," Auger said. "She'll be off-air until we arrive at the other end."

"But I'll be waiting for you," Skellsgard said. "I can still monitor the condition of the link, even if I can't talk to you. I don't think any of us is going to get much sleep in the next thirty hours."

"Don't worry about us," Auger said. "We'll get home safe and dry. Just make sure you're bright-eyed when we pop out the other end. I'll need another ship prepped and ready to make an immediate return trip, and a robot ready to fly it."

"I thought you said you needed medical attention."

"I'm not talking about myself. Floyd can't stay with us on the other side. We still have to get him back into Paris."

Skellsgard nodded. "Yeah, let's try to contain the damage, shall we?"

"I'm all for damage containment," Auger agreed.

"Me, too," Floyd said. "But why do I feel as if I'm the damage?"

"Skellsgard," Auger said. "Listen to me. I think I know why Susan had to die. The stuff they were building in Germany? I think they were parts for a resonant gravity-wave antenna."

"Mmm," she said, frowning. "Tell me more."

"Three spheres dotted around Europe, cooled down close to absolute zero and rigged to vibrate if gravity waves pa.s.s through them."

"You say there are three of these things?"

"One in Berlin, one in Milan, one in Paris. I think they're using three as a means of screening out background noise: any signal registered by all three of them must be significant."

"Three would also give you a handle on direction, if you had accurate enough clocks at all three sites."

"Maybe they have that, too."

"It's still tricky, Auger. You'd need to hang these things in vacuum and hook up some pretty sensitive

acoustic amplifiers before you had a hope in h.e.l.l of getting anything useful out of them."

"But it's all at least feasible using E2 technology, with a few refinements. A lot easier than building

something like a laser interferometer or an orbital test ma.s.s, when no one's invented the laser or the artificial satellite yet." "You have a point there. You know about Weber? Guy from around the same time period as E2. He built a room-temperature bar detector using a chunk of solid aluminium. Same basic principle."

"Did it work?"

"Not really. It wasn't sensitive enough. But the principle was sound, and it paved the way for the cooled-

down resonant detectors that did work, about fifty years later."

"Someone's jumped the gun here," Auger said. "They've built one, maybe even operated it."

"Who do you think is behind it?"

"Slashers. The same ones who must have come through during the Phobos occupation. At the very least,

they're a part of it."

"Why, though? What's the point? We can do all the gravity astronomy we need from the vicinity of the real Earth."

"It isn't about astronomy," Auger said. "I think it's about triangulation."

"You're losing me, Auger."

"Think about it. No kind of electromagnetic radiation can get through the sh.e.l.l of the ALS, which means

that there's no way of determining the real location of E2 in the galaxy. But gravity's different. It seeps through. Now, so do neutrinos, but building a directional neutrino detector is at least as difficult as building a directional gravity-wave antenna, and a lot trickier to keep out of the public eye."

"But why...oh, wait. Now I see. You rig up this thing and start looking for known gravity-wave sources.

Bright high-period derivative binaries: double degenerates on the death spiral, that kind of thing." "Yes," Auger said. "You pick up their resonant frequencies-which are as unique as fingerprints. You measure how strong they are and with three spheres you can calculate which direction they're coming from. You put the pieces together, crunch some data, and you have-"

"The physical co-ordinates of the ALS," breathed Skellsgard.

"They may already have them by now," Auger said.

"But why? Why would anyone go to all that trouble?"

"Because they want to find it very badly," Auger said. "From the outside."

"Jesus," Skellsgard said. "What are they actually thinking of doing with that information?"

"That's the bit that worries me. Look, maybe it's nothing, but for some reason Susan wrote 'Silver Rain'

in one of the letters she intended to send to Caliskan."

Skellsgard said nothing for several seconds. "Jesus squared. Are you sure?"

"I think they might be trying to inject it into the ALS. It's a nano-weapon, so it can't come through the

censor. That only leaves them one option: find the ALS and drill a hole in it."

Skellsgard blew air out through pursed lips. She had no more expletives, no more profanities. "Who do you want me to tell? You reckoned Susan had some doubts about who she could trust." "I think she was right to. I'm taking a risk even talking to you, of course. Now I'm going to take another risk and suggest you get this information to Caliskan as soon as possible."

"I'll do what I can. Like I said, it's not exactly business as usual at this end of the pipe."

"I hear you-just do your best. In the meantime, see if you can check the feasibility of my little theory.

Maybe there's a snag; maybe it can't be a gravity-wave antenna at all."

"I'm on the case," Skellsgard said. "Gives me something to take my mind off the bad news, at least."

"Glad to be of service."

"You take care of yourself, Auger. I still owe you one." Thirty minutes later, they had the ship prepped-as Auger put it-and ready for departure. The cradle had rotated the entire craft through 180 degrees, so that the view through the forward-looking cabin windows showed the gla.s.sy shaft that ran from the main bubble into the wall of the chamber. Beyond the shaft, the walls became mirrored, converging not to infinity but to a kind of iris. The robot had disembarked, slinking away with maggotlike undulations of its pearl-necklace body. Floyd could not see it at all now, but Auger a.s.sured him that it would be attending to the details of their departure, managing several desks at once.

"Skellsgard?" Auger said, from her chair on the left side of the cabin. "You still on the line?"