Her name was Mac Wilson. Her intent was clear, like a piece of crystal.

That was true from the moment her adopted daughter, Barbara, was convicted of the murder of her adopted son, Mian, and sentenced to follow her father — Mae’s husband, Phil — to a room where she would be delivered a lethal injection.

The fact of it was that she’d gotten used to the idea that her husband had been a monster who had abused and killed the boy in their care. Over the years she’d learned to blame Phil, even learned to hate his shade — and, clinging to that, found a little peace.

And she still had Barbara, out there somewhere, a fragment left over from the wreck of her life, proof that some good had come of it all.

But now, because of the WormCam, that wasn’t an option any more. It hadn’t been Phil after all — but Barbara. It just wasn’t acceptable. The monster hadn’t been the one who had lied to her all these years, but one she had nurtured, grown, made.

And she, Mae, wasn’t a victim of deception, but, somehow, an agent of the whole disaster.

Of course to expose Barbara had been just. Of course it was true. Of course it was a great wrong that had been done to Phil, to all of them, in his wrongful conviction, a wrong now put right, at least partially, thanks to the WormCam.

But it wasn’t justice or truth or tightness that Mae wanted. Nobody did. Why couldn’t these people who so loved the WormCam see that? All Mae wanted was consolation.

Her intent was clear from the start, then. It was to find somebody new to hate.

She could never hate Barbara, of course, despite what she’d done. She was still Barbara, bound to Mae as if by a steel cable.

So Mae’s focus shifted, as she deepened and developed her thinking.

At first she had fixed her attention on FBI Agent Mavens, the man who might have found the truth in the first place, in the old pre-WormCam days. But that wasn’t appropriate, of course; he had been, literally, an agent, dumbly pursuing his job with whatever technology had been available to him.

The technology itself, then — the ubiquitous WormCam? But to hate a mere piece of machinery was shallow, unsatisfying.

She couldn’t hate things. She had to hate people.

Hiram Patterson, of course.

He had blighted the human race with his monstrous truth machine, for no purpose she could detect other than profit.

As if incidentally, the machine had even destroyed the religion that had once brought her comfort.

Hiram Patterson.

It took David three days’ intensive work at the Wormworks to link the federal lab’s trace software to an operational wormhole.

Then he went to Bobby’s apartment. He searched it until he found, clinging to a cushion, a single hair from Bobby’s head. He had its DNA sequenced at another of Hiram’s facilities.

The first image, bright and clear in his SoftScreen, was of the hair itself, lying unremarked on its cushion.

David began to track back in time. He had devised a way to make the viewpoint effectively fast-rewind into the past-in reality a succession of fresh wormholes was being established, back along the world-line of DNA molecules from the hair.

He accelerated, days and nights passing in a blur of grey. Still the hair and the cushion sat unchanging at the centre of the image.

There was a flurry of motion.

He backed up, re-established the image, and allowed it to run forward at normal pace.

The date was more than three years in the past. He saw Bobby, Kate, Mary. They were standing, talking earnestly. Mary was half-concealed by a SmartShroud. They were preparing their disappearance, he realized swiftly; already, by this point, they had all three left the lives of David and Heather.

The test was over. The trace worked. He could track forward, approaching the present, until he located Bobby and the others… But perhaps that was best left to Special Agent Mavens.

His test concluded, he prepared to shut down the WormCam — then, on a whim, David arranged the WormCam image so that it centred on Bobby’s face, as if an invisible camera had hovered there, just before his eyes, through the entirety of his young life.

And David began to scan back.

He kept the speed high as the crucial moments of Bobby’s recent life unravelled: at the court with Kate, in the Wormworks with David himself, arguing with his father, crying in Kate’s arms, braving the virtual citadel of Billybob Meeks.

David increased the pace of the rewind further, still fixing on the face of his brother. He saw Bobby eat, laugh, sleep, play, make love. The background, the flickering light of night and day, became a blur, an irrelevant frame to that face; and expressions passed so rapidly across the face that they too became smoothed out, so that Bobby’s face looked permanently in repose, his eyes half-closed, as if he was sleeping. Summer light came and went like tides, and every so often, with a suddenness that startled David, Bobby’s hairstyle would change: from short to long, natural dark to blond, even, at one point, to a shaven-head crewcut.

And, as the years unwound, Bobby’s skin lost the lines he had acquired around his mouth and eyes, and a youthful smoothness lapped over his bones. Imperceptibly at first and then more rapidly, his de-ageing face softened and shrank, as if simplifying, those flickering half-open eyes growing rounder and more innocent, the shadows beyond — of adults and huge, unidentifiable places — more formidable.

David froze the image a few days after Bobby’s birth. The round, formless face of a baby stared out at him, blue eyes wide and empty as windows.

But behind him David did not see the maternity hospital scene he had expected. Bobby was in a place of harsh fluorescents, gleaming walls, elaborate equipment, expensive testing gear and green-coated technicians.

It looked like a laboratory of some kind.

Tentatively, David ran the image forward.

Somebody was holding the infant Bobby in the air, gloved hands under the child’s armpits. With practised ease David swivelled the viewpoint, expecting to see a younger Heather, or even Hiram.

He saw neither. The smiling face before him, looming like the Moon, was of a middle-aged man, greying, skin wrinkled and brown, distinctively Japanese.

It was a face David knew. And suddenly he understood the circumstances of Bobby’s birth, and many other things beside.

He stared at the image a long while, considering what to do.

Mae knew, better maybe than anybody alive, that it wasn’t necessary to injure somebody physically to hurt him.

She hadn’t been directly involved in the horrific crime which had destroyed her family; she hadn’t even been in the city at the time, hadn’t seen so much as a bloodstain. But now everybody else was dead and she was the one who must carry all the hurt, on her own, for the rest of her life.

So to get to Hiram, to make him suffer as she did, she had to hurt the one Hiram loved the most.

It didn’t take much study of Hiram, the most public man on the planet, to figure out who that was. Bobby Patterson, his golden son.

And of course it must be done in such a way that Hiram would know he was responsible, ultimately — just as Mae had been. That was the way to make the hurt deepest of all.

Slowly, in the dark hollows of her mind, she drew up her plans.

She was careful. She had no intention of following her husband and daughter to the cell with the needle. She knew that as soon as the crime was committed the authorities would use the WormCam to scan back through her life, looking for evidence that she’d planned the crime, and for intent.