But he couldn’t live with the knowledge that they might still find him—the time travelers, the tunnel builders, unknown others. Billy didn’t relish living the rest of his years as prey. That was why he had stayed in New York in the first place: to mind the tunnel, check the exits.

Therefore, he could fight.

True, he didn’t know who or what the intruder might be. But maybe that was only a temporary difficulty. Much of his armor’s forensics were still working; Billy guessed he could learn a great deal if he examined the tunnel for clues.

It all depended on the armor, didn’t it?

His lifeline. His life.

At last, he took it out of its hiding place.

He had traded its cardboard box for a wooden chest of approximately two cubic feet in volume—he’d found it in a Salvation Army thrift shop. The chest was closed with a padlock. Billy placed great faith in padlocks; they seemed so much more substantial than the electronic locks of his own era. He wore the key attached to a belt-loop of his pants. Billy lifted the chest from the back of his closet and used the key to open it.

The holes where the lancet and the stylet entered his body had almost healed—but it only hurt for a minute.

He wore loose, layered clothing over the armor to conceal it.

Billy knew how this made him look. He looked like an alcoholic, a bum. Seeing him, people would turn their faces away. But that wasn’t a bad thing.

Underneath, the armor regulated his skin temperature, kept him cool, kept him alert.

The armor was “turned off”—well below full combat capability. But its regulatory functions were automatic. The armor sampled his blood, his nervous impulses. A gland in one of the elytra synthesized new hormones and drip-released them into his body. He was alert, happy, confident.

He was awake.

Life is sleeping, Billy thought. The armor is waking up. Funny how he always forgot this in the long gray passages of his fife; how he remembered it when he put the armor on. It was like coming out of a trance.

All his doubts dissolved. He felt the way he imagined a wolf must feel: fiercely focused and dizzy with the pleasure of the hunt.

He went to the building where his pensioners lived, at the junction of time and time.

He installed two new locks he’d bought at a hardware store yesterday: a new knob set for the door in the lobby and a new padlock for the door farther down. If one of the tenants happened to see him while he was working Billy was prepared to offer an excuse for the way he was dressed—but no one came by except a delivery boy with a box of groceries for Amos Shank, up the stairs and out again without speaking.

Then Billy was in the basement, where no one ever went.

He installed the new padlock and hooked the key to the loop on his belt. Now Billy jingled when he walked.

Then he followed the stone stairs down to the lowest level of the building, the sub-sub-basement where the tunnel began, where one of his concussion grenades had taken out a wall and sealed the empty space behind it—where the rubble had been cleared away again to make a passage.

He didn’t like coming down here. Armor or not, he didn’t like the tunnel. The tunnel made him think of the time ghost he had encountered in it, a mystery even Ann Heath had not been able to explain, a fiery monstrosity with a queasily organic internal structure pulsing under the bright membrane of its skin. Ten years ago now: but the memory was still painfully fresh. The creature had come close enough to singe the hair from the right side of his head. He had smelled the stink of his own burning for days afterward.

Was it a time ghost that had come after him now?

Billy didn’t think so. Ann Heath had said they never appeared outside the tunnels; the tunnels were their habitat; they lived in these temporal fractures the way certain bacteria lived in the scalding heat of volcanic springs. Whatever had come through the door, Billy thought, it must be at least approximately human.

He clambered over the scattered rubble into the mouth of the tunnel. He looked apprehensively into the blank, white distance; but there was no time ghost, not now, and he guessed there probably wouldn’t be; Ann Heath had said they were dangerous but seldom seen. Nevertheless, Billy stayed close to the entranceway. How strange to have made this transition so easily. Billy had damaged the tunnel so that it had a single destination, a house in the Pacific Northwest some thirty years in the future, and he had sealed that entranceway and killed that, time traveler and therefore no one should have come through … but there were footprints in the dust.

Sneaker-prints.

There was a great confusion of these prints and Billy wondered—nervous in the brisk, pale light of the tunnel— whether the intruder might have come from the other direction: discovered the tunnel in Manhattan and followed it into the future.

But no—the lock on the door had been broken from the inside.

Someone who had stumbled onto the tunnel at its other terminus, somewhere near the end of the century?

That was possible—even encouraging. Billy had assumed that gateway was all but unusable; still, after a decade, he supposed someone might have opened it somehow. This new possibility made him more optimistic. He would have to hunt the intruder down and kill him, of course; he needed to be the tunnel’s only proprietor. It was a secret too important to share. But an unsuspecting civilian from the near future would be easy prey.

Still, he shouldn’t count on that. Prepare for hard battle, hope for a vulnerable target.

He cast a final glance down the empty tunnel, then switched on his forensic programs.

He was able to learn a great deal.

His armor detected and memorized fingerprints from the cellar walls, skin samples where the intruder had cut himself on a shard of glass projecting from the rubble. The intruder was quite human, a male, type 0+ blood. Back home, a competent laboratory might have been able to put together a portrait of the man from a simple genome projection, assuming the samples were more or less intact. But Billy didn’t have that capacity; he needed another means of tracking his prey.

The enormity of the task was daunting. It might be impossible—a civilian joyriding from the future might be anywhere. Might have jumped a plane to some familiar place. Invested money in the stock market and set off on a tour of his own recent history.

But the man had arrived here less than a month ago and Billy guessed he would need more time than that to adjust. After all: his money was no good, his knowledge was valuable but difficult to cash in on. He might still be close by.

But how to identify him?

Billy ran a finger through the dust on the floor. Dust from his concussion grenade, dust from the foundation of the building. He opened a pouch in one of the elytra of his armor and withdrew the armor’s headset, a leathery black mask that covered his face entirely. He clipped an optical cable between the headset and the armor’s processors while his forensics sampled the dust and announced its constituents to Billy in a flickering eyepiece readout: limestone, sand, bedrock … and microscopic fragments of the tunnel itself: strange long-chain molecules that fluoresced in dim light, absorbing background radiation and leaking photons.

Billy narrowed the bandwidth of his eyepiece to the frequency of strongest emission, then clambered back into the dark chamber of the basement.

With his opticals adjusted, the dust was plainly luminescent.

He stood in a starry blue limbo, very strange. The tip of his forefinger radiated light like a small constellation.

How much of this dust had the intruder carried out of the building? How much would cling to him? To his shoes? To his clothes? For how long?