She struggled to follow. She had no machete, and the branches and thorns were soon cutting through her thin clothes and into her flesh. It stung, but not too much — of course not. It wasn’t real, just some damn adventure game. She plunged after Bobby, fuming inwardly about decadent technology and excess wealth.

They reached the edge of a clearing, an area of fallen, charred trees within which small green shoots were struggling to emerge. Perhaps this had been cleared by lightning.

Bobby held out an arm, keeping her back at the edge of the forest. “Look.”

An animal was grubbing with snout and paws among the dead, charred wood fragments. It must have been two metres long, with a wolf-like head and protruding canine teeth. Despite its lupine appearance, it was grunting like a pig.

“A cynodont,” whispered Bobby, “A protomammal.”

“Our ancestor?”

“No. The true mammals have already branched off. The cynodonts are an evolutionary dead end… Shit.”

Now there was a loud crashing from the undergrowth on the far side of the clearing. It was a Jurassic Park dinosaur, at least two metres tall; it came bounding out of the forest on massive hind legs, huge jaws agape, scales glittering.

The cynodont seemed to freeze, eyes fixed on the predator.

The dino leapt on the back of the cynodont, which was flattened under the weight of its assailant. The two of them rolled, crushing the young trees growing here, the cynodont squealing.

She shrank back into the jungle, clutching Bobby’s arm. She felt the shaking of the ground, the power of the encounter. Impressive, she conceded.

The carnosaur finished up on top. Holding down its prey with the weight of its body, it bent to the protomammal’s neck and, with a single snap, bit through it. The cynodont was still struggling, but white bones showed in its ripped-open neck, and blood gushed. And when the carnosaur burst the stomach of its prey, there was a stink of rotten meat that almost made Kate retch…

Almost, but not quite. Of course not. Just as, if she looked closely, there was a smooth fakeness to the spurting blood of the protomammal, a glistening brightness to the dino’s scales. Every VR was like this: gaudy but limited, even the stench and noise modelled for user comfort, all of it as harmless — and therefore as meaningless — as a theme-park ride.

“I think that’s a dilophosaur,” murmured Bobby. “Fantastic. That’s why I love this period. It’s a kind of junction of life. Everything overlaps here, the old with the new, our ancestors and the first dinosaurs…”

“Yes,” said Kate, recovering, “But it isn’t real.”

He tapped his skull. “It’s like all fiction. You have to suspend your disbelief.”

“But it’s just some magnetic field tickling my lower brain. This isn’t even the genuine Triassic, for God’s sake, just some academic’s bad guesswork — with a little colour thrown in for the virtual tourist.”

He was smiling at her. “You’re always so angry. Your point is?”

She stared at his empty blue eyes. Up to now he had set the agenda. If you want to get any further, she told herself, if you want to get any closer to what you came for, you’ll have to challenge him. “Bobby, right now you’re lying in a darkened room. None of this counts.”

“You sound as if you’re sorry for me.” He seemed curious.

“Your whole life seems to be like this. For all your talk of VR projects and corporate responsibilities, you don’t have any real control over anything, do you? The world you live in is as unreal as any virtual simulation. Think about it: you were actually alone, before I showed up.”

He pondered that. “Perhaps. But you did show up.” He shouldered his rifle. “Come on. Time for dinner with Dad.” He cocked an eyebrow, “Maybe you’ll stick around even when you’ve got whatever it is you want out of us.”

“Bobby.”

But he had already lifted his hands to his headband.

Dinner was difficult.

The three of them sat beneath the domed apex of Hiram’s mansion. Stars and a gaunt crescent Moon showed between gaps in the racing clouds. The sky could not have been more spectacular — but it struck her that thanks to Hiram’s wormhole DataPipes, the sky was soon going to get a lot more dull, as the last of the low orbit comsats were allowed to fall back into the atmosphere.

The food was finely prepared, as she’d expected, and served by silent drone robots. But the courses were fairly plain seafood dishes of the type she could have enjoyed in any of a dozen restaurants in Seattle, the wine a straightforward Californian Chardonnay. There wasn’t a trace here of Hiram’s own complex origins, no originality or expression of personality of any kind.

And meanwhile, Hiram’s focus on her was intense and unrelenting. He peppered her with questions and supplementaries about her background, her family, her career; over and again she found herself saying more than she should.

His hostility, under a veneer of politeness, was unmistakable. He knows what I’m up to, she realized.

Bobby sat quietly, eating little. Though his disconcerting habit of avoiding eye contact lingered, he seemed more aware of her than before. She sensed attraction — that wasn’t so difficult to read — but also a certain fascination. Maybe she’d somehow punctured that complacent, slick hide of his, as she’d hoped to. Or, more likely, she conceded, he was simply puzzled by his own reactions to her.

Or maybe this was all just fantasy on her part, and she ought to keep from meddling in other people’s heads, a habit she so strongly condemned in others. “I don’t get it,” Hiram was saying now. “How can it have taken until 2033 to find the Wormwood, an object four hundred kilometres across? I know it’s out beyond Uranus, but still.”

“It’s extremely dark and slow moving,” said Kate. “It is apparently a comet, but much bigger than any comet known. We don’t know where it came from; perhaps there is a cloud of such objects out there, somewhere beyond Neptune.

“And nobody was especially looking that way anyhow. Even Spaceguard concentrates on near-Earth space, the objects which are likely to hit us in the near future. The Wormwood was found by a network of sky-gazing amateurs.”

“Umm,” said Hiram. “And now it’s on its way here.”

“Yes. In five hundred years.”

Bobby waved a strong, manicured hand. “But that’s so far ahead. There must be contingency plans.”

“What contingency plans? Bobby, the Wormwood is a giant. We don’t know any way to push the damn thing away, even in principle. And when that rock falls, there will be nowhere to hide.”

“We don’t know any way?” Bobby said dryly.

“I mean the astronomers.”

“The way you were talking I’d almost imagined you discovered it yourself.” He was needling her, responding to her earlier probing. “It’s so easy to mix up one’s own achievement with that of the people one relies on, isn’t it?”

Hiram was cackling. “I can tell you kids are getting on just fine. If you care enough to argue… And you, of course, Ms. Manzoni, think the people have a right to know that the world is going to end in five hundred years?”

“Don’t you?”

Bobby said, “And you’ve no concern for the consequences — the suicides, the leap in abortion rates, the abandonment of various environment-conservation projects?”

“I brought the bad news,” she said tensely. “I didn’t bring the Wormwood. Look, if we aren’t informed, we can’t act, for better or ill; we can’t take responsibility for ourselves — in whatever time we have left. Not that our options are promising. Probably the best we can do is send a handful of people off to somewhere safer, the Moon or Mars or an asteroid. Even that isn’t guaranteed to save the species, unless we can establish a breeding population. And,” she said heavily, “those who do escape will no doubt be those who govern us, and their offspring, unless we shake off our electronic anaesthesia.”