"How's Caloris?" Larionova asked.

Well, we don't have much to report yet. We decided to start with a detailed gravimetric survey...

"And?"

We found the impact object. We think. It's as massive as we thought, but much -- much -- too small, Irina. It's barely a mile across, way too dense to be a planetesimal fragment.

"A black hole?"

No. Not dense enough for that.

"Then what?"

Wu looked exasperated. We don't know yet, Irina. We don't have any answers. I'll keep you informed.

Wu closed off the link.

Standing on the corona-lit wall of Chao Meng-Fu Crater, Larionova asked Kevan Scholes about Caloris.

"Caloris is big," he said. "Luna has no impact feature on the scale of Caloris. And Luna has nothing like the Weird Country in the other hemisphere..."

"The what?"

A huge planetesimal -- or something -- had struck the equator of Mercury, five billion years ago, Scholes said. The Caloris Basin -- an immense, ridged crater system -- formed around the primary impact site. Whatever caused the impact was still buried in the planet, somewhere under the crust, dense and massive; the object was a gravitational anomaly which had helped lock Mercury's rotation into synchronization with its orbit.

"Away from Caloris itself, shock waves spread around the planet's young crust," Scholes said. "The waves focused at Caloris' antipode -- the point on the equator diametrically opposite Caloris itself. And the land there was shattered, into a jumble of bizarre hill and valley formations. The Weird Country... hey. Dr. Larionova."

She could hear that damnable grin of Scholes's. "What now?" she snapped.

He walked across the summit towards her. "Look up," he said.

"Damn it, Scholes--"

There was a pattering against her face plate.

She tilted up her head. Needle-shaped particles swirled over the wall-mountain from the planet's dark side and bounced off her face plate, sparkling in corona light.

"What in Lethe is that?"

"Snow," he said.

Snow... on Mercury?

In the cool darkness of the tunnel, the people clambered over each other; they bumped against the Ice walls, and their muttering filled the water with criss-crossing voice-ripples. Cilia-of-Gold swam through and around the crowd, coaxing the people to follow her will.

She felt immensely weary. Her concentration and resolve threatened continually to shatter under the Seeker's assault. And the end of the tunnel, with the deadly Heads beyond, was a looming, threatening mouth, utterly intimidating.

At last the group was ready. She surveyed them. All of the people -- except the very oldest and the very youngest -- were arranged in an array which filled the tunnel from wall to wall; she could hear flukes and carapaces scraping softly against Ice.

The people looked weak, foolish, eager, she thought with dismay; now that she was actually implementing it her scheme seemed simple-minded. Was she about to lead them all to their deaths?

But it was too late for the luxury of doubt, she told herself. Now, there was no other option to follow.

She lifted herself to the axis of the tunnel, and clacked her mandibles sharply.