With a few keystrokes she restored the scene.

It was a small garden — a yard, really, strips of sun-baked grass separated by patches of gravel, a few poorly tended flower beds. The image was bright, the sky blue, the shadows long. There were toys everywhere, splashes of colour, some of them autonomously toiling back and forth on their programmed tasks and routines.

Here came two children: a boy and a girl, aged maybe six and eight respectively. They were laughing, kicking a ball between them, and they were being chased by a man, also laughing. He grabbed the girl and whirled her high in the air, so that she flew through shadows and light. Mary froze the scene.

“A cliché,” she said. “Right? A childhood memory, a summer’s afternoon, long and perfect.”

“This is your father and your brother — and yourself.”

Her face twisted into a sour smile. “The scene is barely eight years old, but two of the protagonists are dead already. What do you think of that?”

“Mary.”

“You wanted to see my software.”

He nodded. “Show me.”

She tapped at the ’Screen; the viewpoint panned from side to side, and stepped forward and back in time, through a few seconds. The girl was raised and lowered and raised again, her hair tumbling this way and that, as if this was a film being wound back and forth.

“Right now I’m using the standard workstation interface. The viewpoint is like a little camera floating in the air. I can control its location in space and move it through time, adjusting the position of the wormhole mouth. Which is fine for some applications. But if I want to scan more extended periods, it’s a drag — as you know.”

She let the scene run on. The father put down child-Mary. Mary focused the viewpoint on her father’s face and, with taps of the SoftScreen, tracked it, jerkily, as the father ran after his daughter across that vanished lawn. “I can follow the subject,” she said clinically, “but it’s difficult and tedious. So I’ve been seeking a way to automate the tracking.” She tapped more virtual buttons. “I used pattern-recognition routines to latch on to faces. Like his.”

The WormCam viewpoint swung down, as if guided by some invisible cameraman, and focused on her father’s face. The face stayed there, central to the image, as he moved his head this way and that, talking, laughing, shouting; the background swung around him disconcertingly.

“All automated,” David said. “Yes. I have subroutines to monitor my preferences, and make the whole thing a little more professional…” More keystrokes, and now the viewpoint pulled back a little. The camera angles were more conventional, stabilized, no longer slaved to that face. The father was still the central protagonist, but his context became more clear.

David nodded. “This is valuable, Mary. This, tied to interpretative software, might even allow us to automate the compilation of historic-figure biographies, at first draft anyhow. You’re to be commended.”

She sighed. “Thanks. But you still think I’m a wacko because I’m watching my father rather than John Lennon. Don’t you?”

He shrugged. He said carefully, “Everybody else is watching John Lennon. His life. for better or worse, is common property. Your life — this golden afternoon — is your own.”

“But I’m an obsessive. Like those nuts you find watching their own parents making love, watching their own conception.”

“I’m no psychoanalyst,” he said gently. “Your life has been hard. Nobody denies that. You lost your brother, your father. But…”

“But what?”

“But you’re surrounded by people who don’t want you to be unhappy. You have to believe that.”

She sighed heavily. “You know, when we were little — Tommy and I — my mother had a habit of using other adults against us. If I was bad, she’d point to something in the adult world — a car sounding its horn a kilometre away, even a jet airplane screaming overhead — and she’d say, ‘That man heard what you said to your mother, and he’s showing you what he thinks about it.’ It was terrifying. I grew up with the impression that I was alone in a huge forest of adults, all of whom watched over me, judging me the whole time.”

He smiled. “Full-time surveillance. Then you won’t find it hard to get used to life with the WormCam.”

“You mean, the damage has been done to me already? I’m not sure that’s a consolation.” And then she eyed him. “So, David — what do you watch when you have the WormCam to yourself?”

He went back to his apartment. He slaved his own workstation to Mary’s back at the Wormworks, and ran through the recordings OurWorld routinely made of every user’s utilization of its WormCams.

He’d done enough, he felt, not to feel guilty over what he had to do next to fulfill his obligation to Heather. Which was to spy on Mary.

It didn’t take him long to get to the heart of it. She did, after all, view the same incident, over and over.

It had been another bright afternoon of sun and play and family, not long after the one he’d watched with her. Here she was at age eight with her father and family, hiking — easily, at a six-year-old’s pace — through the Rainier National Park. Sunlight, rock, trees.

And then he came to it: the crux of Mary’s life. It lasted only seconds.

It wasn’t as if they’d taken any risks; they hadn’t strayed from the marked path, or attempted anything ambitious. It had just been an accident

Tommy had been riding his father’s neck, clinging to handfuls of thick black hair, with his legs draped over his shoulders, firmly grasped by his father’s broad hands. Mary had gone running past, eager to chase what looked like the shadow of a deer. Tommy reached for her, unbalancing a little, and the father’s grasp slipped — just a little, but enough.

The impact itself was unspectacular: a soft crack as that big skull hit a sharp volcanic rock, the strange limp crumpling of the body. Just unfortunate, even in the way he hit the ground so lethally. Nobody’s fault.

That was all. Over in a heartbeat. Unfortunate, commonplace, nobody’s fault — save, he thought with unwelcome anger, the Cosmic Designer who chose to lodge something as precious as the soul of a six-year-old in a container so fragile.

The first time Mary (and now David, like an unwelcome ghost) had watched this incident, she’d used a remarkable WormCam viewpoint: looking out through child-Mary’s own eyes. It was as if the viewpoint was lodged right at the centre of her soul, that mysterious place in her head where “she” resided, surrounded by the soft machinery of her body.

Mary saw the boy falling. She reacted, reached out her arms, took a pace toward him. He seemed to fall slowly, as if in a dream. But she was too far away to reach him, could do nothing to change what unfolded.

…And now, tracking Mary’s usage, David was forced to watch the same incident from the father’s point of view. It was like looking down from a watchtower, with child-Mary a blur below him, the boy a thing of dark shadows around his head. But the same events unfolded with grisly inevitability: the unbalancing, the slip, the boy falling, his legs impeding him so that he fell upside down and descended headfirst toward the stony ground.

But what Mary watched over and over, obsessively, was not the death itself, but the moments before. Little Tommy, falling, was only a meter from Mary, but that was too far, and no more than centimetres from his father’s grasp, a fraction of a second’s reaction time. It might have been a kilometre, hours of delay; it would have made no difference.

And this, David suspected, was the real reason her father had committed his suicide. Not the publicity that suddenly surrounded him and his family — though that couldn’t have helped. If he was anything like Mary, he must have seen immediately the implications of the WormCam for himself — just like millions of others, now exploring the capabilities of the WormCam, and the darkness in their own hearts.