The game trail helped, but it was far from straight, and many of its slopes were almost vertical. Tamman took the lead while Sean brought up the rear. The formation freed Harriet and Sandy to focus on their scanpacks (which had far more reach than implant sensors), without worrying about anything they might meet, and the four of them moved at a pace which would have reduced any unenhanced human to gasping exhaustion in minutes.

The moon was still high when Harriet threw up a hand and beckoned them all to a halt. Sean closed up from behind as the other three clustered to wait for him, and his eyes brightened as he looked down at last into the valley they'd come so far to find.

It was bigger than he'd expected—at least twenty kilometers across at its widest point and winding deep into the mountains. A sharp bend fifteen kilometers to the north blocked their vision, and the shallow, rushing river down its length gleamed dull pewter under the moon. He adjusted his eyes to telescopic vision and felt a shiver of excitement. The shapes clumped on either bank of the river at mid-valley were half-buried in drifted ages of soil, but they were too regular and vertical to be natural.

"I'm getting those same readings." Harriet swung the hand-held array of her passive backpack unit slowly from side to side and frowned. "There's a batch of new ones, too. They're lots weaker and more spread out; that's probably why we didn't spot them before."

Sandy turned, directing her own attention down-valley, and nodded.

"You're right, Harry. Most of what we saw before seems to be clustered in those ruins, but I'm getting a line of weak point sources about ten klicks to the south. Looks like they run clear across the valley."

"Yeah." Harriet shaded her eyes with her free hand as if it could help her see farther. "And there's another line just like it up there where the valley curls back to the west. I'm not too sure I like that. I can't lock in well enough to prove it, but they could be passive sensors, and those're logical places to put some sort of defensive system."

"Good point," Sandy agreed.

"Um." Sean moved a few meters south, peering in the direction of Sandy's find, but not even enhanced eyes could pick out any details. The valley floor was too heavily covered in scrub trees and tall alpine grasses, and moonlight and shadow did funny things to depth perception even in low-light mode. He pinched his nose in thought, then turned back to the others.

"Anything right in front of us?" he asked, pointing down the steep-sloped valley wall, and his sister shook her head.

"Not on this side, but that big one's just about opposite us. And I'm getting something else from it now. Do you have it, Sandy?"

"No, I—oh. That's funny." She made painstaking adjustments. "The darn thing isn't steady, almost like it's got some sort of intermittent short." It was her turn to frown. "See how the beacon power level fluctuates just a bit in time with it? Think it's some kind of control system?"

"If it is, it looks kind of senile. Then again, from the state of the ruins this whole place must've been abandoned thousands of years ago." Harriet tinkered with her own scanpack, then shrugged. "Let's spread out a little and see if we can triangulate on it, Sandy. I'd feel better if I at least knew exactly where whatever-it-is is."

"Suits me." The two of them separated and took very careful bearings, and Sandy nodded and pointed across the valley.

"Okay, I see it... sort of," she said, and Sean stood behind her and followed the line of her finger until he saw the more solid patch of shadows. He couldn't make out much in light-gathering mode, but when he switched to infrared things popped into better resolution. Not a lot better, but better. The ruins were built out from a bare stone precipice and whatever they were made of had different thermal properties from the cliff. Small trees sprouted from a thick roof of collected dirt, but the vertical walls were clear.

"Any better ideas about that intermittent source now that you know where it is?" he asked, but Sandy shook her head. He glanced at Harriet and sighed as he got a shrug of equal mystification. "That's what I was afraid of. Well, whatever else this is, it's clearly the leftovers of some Imperial site, and I'm not too surprised it's in such lousy shape. In fact, if I'm surprised at all it's that anything's live down there. But it looks like we have to go on down if we want any more to go on. Any objections?"

There were none, though Harriet looked a bit dubious, and he nodded.

"Okay, but we'll play this as smart as we can. Let's rope up, Tam, and since you're the closest we've got to a Marine, you take point. Sandy, you stay up here and play lookout till the rest of us get down. Keep an eye on the whole place, but especially on that thing on the far side. Harry, you follow Tam with your scanpack, and I'll bring up the rear."

Tamman nodded and slid out of his pack to extract a two hundred-meter coil of synthetic rope. While he and Sean rigged safety harnesses, Harriet and Sandy went on trying to analyze their readings without much success. Sean wasn't too happy about that, yet there wasn't a lot he could do about it, and he waved Tamman over the side.

Tamman picked his way as carefully as he could, but the hundred-meter slope, while less sheer than the bare rock face to the west, was both steep and treacherous. The soil was soft and shifting despite a covering of grass, and he slipped several times. Harriet had it easier. She was taller than he but as slender as her mother; even with her scanpack she was much lighter, and she had the advantage of watching where he'd put his feet ahead of her.

Sean should have found the descent easiest of all, despite his height and weight, since he was behind both of them and placed to learn by their mistakes, but much as he knew he ought to, he couldn't seem to keep his mind on where he was going. He kept looking up at the ruins on the far side of the valley, and when he wasn't doing that his attention kept trying to stray to the ones out in the middle. He knew he should ignore them—after all, Sandy was keeping watch on them and he was anchor man for the safety rope—but he just couldn't. Which was another reason he'd put Tamman in front, where they needed someone who wouldn't let curiosity distract him from the task in hand.

Yet perhaps it was as well he was distracted. It meant he was looking up, not at his feet, when Sandy suddenly screamed.

"Something's coming up over th—!"

A boulder two meters to Harriet's right exploded, and she cried out in pain as a five-kilo lump of stone slammed into her shoulder. It didn't break her bio-enhanced skin, but the impact threw her from her feet, and that, Sean realized later, was what saved her life. The heavy energy gun needed a handful of seconds to reduce the boulder to powder; by the time the first energy bolt hit where she'd been standing, she wasn't there anymore.

He dug in his heels instinctively, hurling himself backward to anchor her, but the next bolt of gravitonic disruption sliced the rope like a thread. Her fall accelerated, and she tumbled downslope, slithering and bouncing. She tried frantically to avoid Tamman, clawing for traction as she gathered speed, but the loose soil betrayed her and he couldn't get out of the way in time. Her careening body cut his feet from under him, sending them both crashing downward in a confusion of arms and legs, and more bolts of energy came screaming out of the night. Gouts of flying dirt erupted all about them as ancient, erratic tracking systems tried to lock on them, and only their unpredictable movement and the senility of the defenses kept them alive.

Sean almost fell after them as soil crumbled under his heels, but he managed to hold his position, and his grav gun leapt into his hands in pure reflex. The scarcely visible energy gun fire was a terrible network of fury to his enhanced vision, and a fist squeezed his heart as it reached out for his sister and his friend. But he'd been looking in exactly the right direction when it started. Whatever was firing on them wasn't shooting at him—apparently he was still outside its programmed kill zone—but his implants told him where its targeting systems were, and his weapon snapped up into firing position without conscious thought.