"Are we going to leave the Earth?" Marty asked. The adults around him visibly cringed.

"Shhh," the young woman said, maneuvering her way past him. "Wait and see."

Arthur reached out and gently pinched Marty's ear between thumb and forefinger. Smart boy, he thought. He looked out across the water, feeling the bay's white-caps thump rhythmically against the boat hull. Several people were becoming seasick. A nut-brown, gray-bearded man of about forty came down from the pilot house and passed out plastic bags. "Use them," he said gruffly. "Everybody. We don't need anybody sicker than they have to be, and we certainly don't need chain reactions."

Arthur surveyed the city's skyline, blinking at the salt spray. All that work. Around the world. Thousands of years. He could not even begin to encompass the enormity. Francine came to him and wrapped her arms around him tightly. He leaned his cheek against her hair, not daring to feel as optimistic as he wanted to be.

"Can you tell me what's going on now?" she asked.

Marty snuggled up to them. "We're going away, Mom," he said.

"Are we?" she asked Arthur.

He swallowed and barely moved his head, then nodded. "Yes. I think we are."

"Where?"

"I don't know."

They cut through the water under the San Francisco-Oakland Bay Bridge, Yerba 3uena Island and Treasure Island to their right, tall mounds of dark green and brown on the slate-colored, white-flecked waters.

"See, Marty?" Francine said, pointing up at the bridge's maze of girders and the huge piers and tower legs. "We drove over that just a while ago."

Marty gave the wonder cursory attention. The sea was getting rougher. Alcatraz, a desolate rock cluttered with ancient buildings, a water tower prominent, lay dead ahead. The boat slowed, its motors cutting back to a steady chug-chug-chug. The young woman passed among them again, examining everybody closely for unnecessary belongings. Nobody protested; they were either numb with fear, seasick, exhausted, or all three. She smiled at Marty in passing to the rear again.

The boat stopped, drifting in the chop. The passengers began to murmur. Then Arthur saw something square and gray rise beyond the port gunwale. He thought immediately of a submarine sail, but it was much smaller, barely as wide as a double doorway and no more than ten feet out of the water.

"We'll have to be careful," the woman told them, standing on a short ladder near the pilot house. "The water's rough. We're all going to climb down through this doorway." An empty black square appeared in the gray block. "There's a spiral staircase going down into the ship. The ark. If you have a child younger than twelve, please hold its hand and be very careful."

A burly fisherman in a black turtleneck sweater struggled to extend a short gangplank to the block's entrance.

"We are leaving," Francine said, her voice like a girl's.