Lake waited and watched until he was sure the unicorns were gone for good. Then he ordered the all clear given and hurried to the south wall, to look down across the barren valley and hope he would not see what he expected to see.

Barber came up behind him, to sigh with relief. “That was close. It’s hard to make so many people stay absolutely quiet for hour after hour. Especially the children⁠—they don’t understand.”

“We’ll have to leave,” Lake said.

“Leave?” Barber asked. “We can make this stockade strong enough to hold out unicorns.”

“Look to the south,” Lake told him.

Barber did so and saw what Lake had already seen; a broad, low cloud of dust moving slowly toward them.

“Another herd of unicorns,” Lake said. “John didn’t know they migrated⁠—the Dunbar Expedition wasn’t here long enough to learn that. There’ll be herd after herd coming through and no time for us to strengthen the walls. We’ll have to leave tonight.”

Preparations were made for the departure; preparations that consisted mainly of providing each person with as much in the way of food or supplies as he or she could carry. In the 1.5 gravity, that was not much.

They left when the blue star rose. They filed out through the northern gate and the rear guard closed it behind them. There was almost no conversation among them. Some of them turned to take a last look at what had been the only home they had ever known on Ragnarok, then they all faced forward again, to the northwest, where the foothills of the plateau might offer them sanctuary.

They found their sanctuary on the second day; a limestone ridge honeycombed with caves. Men were sent back at once to carry the food and supplies left in the stockade to the new home.