“It was incredible,” the girl said. “We were monitoring the changes. Tee, pee, rho, all went off the scale—”

“Temperature, pressure, density,” Henry said drily. “Jane, meet Marge Case.”

Marge Case just kept talking. “ — and when we replayed the bang we detected gamma rays, X-rays—”

“Like Venus,” Jane said.

“Maybe,” Henry said. “More like fusion products, from the layers around the very centre.”

Jane looked back at the case; there was no sign of the Moon rock. “Where is it now? Converted to energy?”

“Oh, no.” The girl laughed, and Jane could have happily struck her. “Only a fraction of the mass was destroyed, we think. Maybe one part in ten to power eleven.”

Henry thought about that. “If it was all hydrogen, that would be a sphere maybe forty microns across. At fusion temperatures and pressures.”

Jane said, “And the rest of the Moon rock—”

“Is gone,” Henry said grimly. “Converted.”

“To Moonseed?”

“Some of it. We’ll find it if we scrape the walls, no doubt.”

“It’s just incredible,” said Marge Case. Think of it. We probably had higher-order string modes, here, in this lab.”

“For a squillionth of a second,” Henry said.

“But why?” Jane asked. “Why does it do this?”

Henry shrugged. “To propagate. The Moonseed will go on to infect normal matter, create more puffball-fungus explosions, and propagate further still.”

“Like what’s happening outside.”

“We think so,” Henry said. “Although the growth isn’t even. Olivine-rich basalt is the raw material of choice…”

Jane looked from one to the other. “I don’t understand you. You seem — excited.”

“Exhilarated,” Marge Case said.

“Really?”

“Of course.” Her eyes were moist, shining in the imperfect light. “Don’t you see? It’s not just the high-energy physics. This is the discovery of the century. This may be life from another world. An utterly different mode of biology.” She looked, to Jane, as if she hadn’t slept for days, as if she’d been living on adrenaline.

“What I mostly feel is frustrated,” Henry said. “We have no time to do the science. A study like this should take years. Teams all around the world. We’re doing little more than guesswork, here. And—”

“What else?”

“…Awe, I guess,” he said. “Geologists get used to thinking big. Big timescales, huge energies, gigantic events. But I’m not used to seeing all that intrude into my own life.”

“But we’re talking about a threat to the city,” Jane said. “Screw this guff about biology and science.”

“Jane—”

“You think I’m being hysterical. But somebody needs to express what we’re really saying, here. This isn’t just some intellectual puzzle.”

Marge smiled sadly. “Isn’t it?”

Jane watched Henry. “I need to get out of here. I have to find my family.” And, here was the unspoken thought, I could use your help.

He was meeting her eyes. But now there was hesitation.