The doughnut didn't look any different from this position, a glowing ring surrounding the grey pressure membrane. Marcus put one foot over the edge of the exotic matter, and jumped.
   He fell clean through the pressure membrane. There was no gravity field in the wormhole, although every movement suddenly became very sluggish. To his waving limbs it felt as if he was immersed in some kind of fluid, though his sensor block reported a perfect vacuum.
   The wormhole wall was insubstantial, difficult to see in the meagre backscatter of light from the pressure membrane. Five narrow lines of yellow light materialized, spaced equidistantly around the wall. They stretched from the rim of the pressure membrane up to a vanishing point some indefinable distance away.
   Nothing else happened. Marcus drifted until he reached the wall, which his hand adhered to as though the entire surface was one giant stikpad. He crawled his way back to the pressure membrane. When he stuck his hand through, there was no resistance. He pushed his head out.
   There was no visible difference to the chamber outside. He datavised his communication block to search for a signal. It told him there was only the band from one of the relay blocks in the stairwells. No time had passed.
   He withdrew back into the wormhole. Surely the xenocs hadn't expected to crawl along the entire length? In any case, the other end would be thirteen thousand years ago. Marcus retrieved the xenoc activation code from his neural nanonics, and datavised it.
   The lines of light turned blue.
   He quickly datavised the deactivation code, and the lines reverted to yellow. This time when he emerged out into the portal chamber there was no signal at all.
 
   • • •
 
   «That was ten hours ago,» Marcus told his crew. «I climbed out and walked back to the ship. I passed you on the way, Karl.»
   «Holy shit,» Roman muttered. «A time machine.»
   «How long was the wormhole active for?» Katherine asked.
   «A couple of seconds, that's all.»
   «Ten hours in two seconds.» She paused, loading sums into her neural nanonics. «That's a year in thirty minutes. Actually, that's not so fast. Not if they were intending to travel a couple of thousand years into the future.»
   «You're complaining about it?» Roman asked.
   «Maybe it speeds up the further you go through it,» Schutz suggested. «Or more likely we need the correct access codes to vary its speed.»
   «Whatever,» Marcus said. He datavised the flight computer and blew the tether bolts which were holding Lady Mac to the wreckage. «I want flight-readiness status, people, please.»
   «What about Jorge and the others?» Karl asked.
   «They only come back on board under our terms,» Marcus said. «No weapons, and they go straight into zero-tau. We can hand them over to Tranquillity's serjeants as soon as we get home.» Purple course vectors were rising into his mind. He fired the manoeuvring thrusters, easing Lady Mac clear of the xenoc shell.
 
   • • •
 
   Jorge saw the sparkle of bright dust as the explosive bolts fired. He scanned his sensor collar round until he found the tethers, narrow grey serpents flexing against the speckled backdrop of drab orange particles. It didn't bother him unduly. Then the small thrusters ringing the starship's equator fired, pouring out translucent amber plumes of gas.
   «Katherine, what do you think you're doing?» he datavised.
   «Following my orders,» Marcus replied. «She's helping to prep the ship for a jump. Is that a problem for you?»
   Jorge watched the starship receding, an absurdly stately movement for an artifact that big. His respirator tube seemed to have stopped supplying fresh oxygen, paralysing every muscle. «Calvert. How?» he managed to datavise.
   «I might tell you some time. Right now, there are a lot of conditions you have to agree to before I allow you back on board.»
   Pure fury at being so completely outmanoeuvred by Calvert made him reach automatically for his weapon. «You will come back now,» he datavised.
   «You're not in any position to dictate terms.»
   Lady Macbeth was a good two hundred metres away. Jorge lined the stubby barrel up on the rear of the starship. A green targeting grid flipped up over the image, and he zeroed on the nozzle of a fusion-drive tube. He datavised the X-ray laser to fire. Pale white vapour spewed out of the nozzle.
 
   • • •
 
   «Depressurization in fusion drive three,» Roman shouted. «The lower deflector coil casing is breeched. He shot us, Marcus, Jesus Christ, he shot us with an X-ray.»
   «What the hell kind of weapon has he got back there?» Karl demanded.
   «Whatever it is, he can't have the power capacity for many more shots,» Schutz said.
   «Give me fire control for the maser cannons,» Roman said. «I'll blast the little shit.»
   «Marcus!» Katherine cried. «He just hit a patterning node. Stop him.»
   Neuroiconic displays zipped through Marcus's mind. Ship's systems coming on-line as they shifted over to full operational status, each with its own schematic. He knew just about every performance parameter by heart. Combat-sensor clusters were already sliding out of their recesses. Maser cannons powering up. It would be another seven seconds before they could be aimed and fired.
   There was one system with a faster response time.
   «Hang on,» he yelled.
   Designed for combat avoidance manoeuvres, the fusion-drive tubes exploded into life two seconds after he triggered their ignition sequence. Twin spears of solar-bright plasma transfixed the xenoc shell, burning through deck after deck. They didn't even strike anywhere near the airlock which Jorge was cloistered in. They didn't have to. At that range, their infra-red emission alone was enough to break down his SII suit's integrity.
   Superenergized ions hammered into the wreck, smashing the internal structure apart, heating the atmosphere to an intolerable pressure. Xenoc machinery detonated in tremendous energy bursts all through the structure, the units expending themselves in spherical clouds of solid light which clashed and merged into a single wavefront of destruction. The giant rock particle lurched wildly from the explosion. Drenched in a cascade of hard radiation and subatomic particles, the unicorn tower at the centre of the dish snapped off at its base to tumble away into the darkness.
   Then the process seemed to reverse. The spume of light blossoming from the cliff curved in on itself, growing in brightness as it was compressed back to its point of origin.
   Lady Mac 's crew were straining under the five-gee acceleration of the starship's flight. The inertial-guidance systems started to flash priority warnings into Marcus's neural nanonics.
   «We're going back,» he datavised. Five gees made talking too difficult. «Jesus, five gees and it's still pulling us in.» The external sensor suite showed him the contracting fireball, its luminosity surging towards violet. Large sections of the cliff were flaking free and plummeting into the conflagration. Black lightning cracks were splitting open right across the rock.
   He ordered the flight computer to power up the nodes and retract the last sensor clusters.
   «Marcus, we can't jump,» Katherine datavised, her face pummelled into frantic creases by the acceleration. «It's a gravitonic emission. Don't.»
   «Have some faith in the old girl.» He initiated the jump.
   An event horizon eclipsed the Lady Macbeth 's fuselage.
   Behind her, the wormhole at the heart of the newborn micro-star gradually collapsed, pulling in its gravitational field as it went. Soon there was nothing left but an expanding cloud of dark snowdust embers.
 
   • • •
 
   They were three jumps away from Tranquillity when Katherine ventured into Marcus's cabin. Lady Mac was accelerating at a tenth of a gee towards her next jump coordinate, holding him lightly in one of the large black-foam sculpture chairs. It was the first time she'd ever really noticed his age.
   «I came to say sorry,» she said. «I shouldn't have doubted.»
   He waved limply. «Lady Mac was built for combat, her nodes are powerful enough to jump us out of some gravitonic field distortions. Not that I had a lot of choice. Still, we only reduced three nodes to slag, plus the one dear old Jorge damaged.»
   «She's a hell of ship, and you're the perfect captain for her. I'll keep flying with you, Marcus.»
   «Thanks. But I'm not sure what I'm going to do after we dock. Replacing three nodes will cost a fortune. I'll be in debt to the banks again.»
   She pointed at the row of transparent bubbles which all held identical antique electronic circuit boards. «You can always sell some more Apollo command module guidance computers.»
   «I think that scam's just about run its course. Don't worry, when we get back to Tranquillity I know a captain who'll buy them from me. At least that way I'll be able to settle the flight pay I owe all of you.»
   «For Heaven's sake, Marcus, the whole astronautics industry is in debt to the banks. I swear I never could understand the economics behind starflight.»
   He closed his eyes, a wry smile quirking his lips. «We very nearly solved human economics for good, didn't we?»
   «Yeah. Very nearly.»
   «The wormhole would have let me change the past. Their technology was going to change the future. We could have rebuilt our entire history.»
   «I don't think that's a very good idea. What about the grandfather paradox for a start? How come you didn't warn us about Jorge as soon as you emerged from the wormhole?»
   «Scared, I guess. I don't know nearly enough about quantum temporal displacement theory to start risking paradoxes. I'm not even sure I'm the Marcus Calvert that brought this particular Lady Macbeth to the xenoc wreck. Suppose you really can't travel between times, only parallel realities? That would mean I didn't escape into the past, I just shifted sideways.»
   «You look and sound pretty familiar to me.»
   «So do you. But is my crew still stuck back at their version of the wreck waiting for me to deal with Jorge?»
   «Stop it,» she said softly. «You're Marcus Calvert, and you're back where you belong, flying Lady Mac
   «Yeah, sure.»
   «The xenocs wouldn't have built the wormhole unless they were sure it would help them get home, their true home. They were smart people.»
   «And no mistake.»
   «I wonder where they did come from?»
   «We'll never know, now.» Marcus lifted his head, some of the old humour emerging through his melancholia. «But I hope they got back safe.»