Perfect Fit

"David's dead!"

The illicit words escaped into the sterile air of the culture chamber.

Roz's stomach clenched and she clapped a hand over her mouth, simultaneously squeezing her nostril flaps shut. Her eyes raked the splicing lab, visible through the transparent sheet wall. Had anybody heard?

More crucially, had she expelled any germs along with her words? Most pathogens had been eliminated from the closed environment before the worldship left Earth, but a small number had hitched a ride, and it was their presence that required Roz's specific genetic modification-the nostril flaps of the grey seal-which sealed her breath within her lungs for as long as she worked inside the chamber.

And now one startled exclamation might have brought ruin to the twenty fragile lives under her care. All she could do was hope that luck was on her side. So far it smiled upon her-no one had looked her way, her misdemeanour going unremarked.

If only she could be as fortunate with the microbes.

With trembling hands, she raised the dish of nutrient gel to eye level. The eight shrivelled cells that had once been a viable embryo were too small for her to see with her naked vision, but under the lens she used for stem cell harvesting, the evidence had been painfully clear; there was no coming back from that level of desiccation.

But why? Roz was certain she'd programmed the nutrient stream correctly; it wasn't as if this was the first time she'd prepared a source embryo for harvest; it was an integral part of her working life.

Cycling back through decon with the dish still in her hand seemed to take forever, and before she was through, someone noticed. By the time she stepped back into the lab proper, all the techs had gathered around, shock and sorrow dragging their faces down.

"Is that...?"

She nodded, a tear trickling down her cheek. "Yes, it's David. I've no idea why."

Her supervisor, Splicer Chao-xing, pushed through the crowd, anger pinching the small woman's delicate features. Roz cringed.

"You must have made a mistake," Chao-xing accused. "Did you check the nutrient levels?"

Roz's hands shook even harder, and someone gently removed the dish containing the dead embryo from her grasp before she could drop it. With stiff shoulders, Roz marched over to her work station and pointed at the readouts.

"See? No mistake."

Chao-xing leaned in close to study the control panel, her jaw tightening when she found nothing to criticise. She moved to the next console where she made a deliberate show of inspecting the levels of the hormone mix being fed into the general water supply. The concoction, which kept the GM population of the worldship sterile, was on a completely separate system, and could never have contaminated the embryos' discrete nutrient supply, but she checked it anyway.

"Hmph. There must be an explanation." She glared up at Roz, intimidating despite standing only as tall as Roz's shoulder. "Find it," she ordered, and stormed back to her work, the many slender tendrils she possessed in place of fingers knotting in a visible display of annoyance.

Roz shook her head and wondered, not for the first time, how someone so small could be so menacing.

When Roz had first entered the hallowed world of the gene splicers as a young tech assistant, she'd been wide-eyed with awe, and proud that she'd been designed to be a part of the worldship's elite and not one of its menials. Even better, she was part of the generation-gen 312-that was destined to oversee the resurrection of the human race, just as soon as the worldship made landfall on the promised planet.