The cubs whimpered louder.

“They want to go to her, but they’re afraid of the ice,” whispered Jack.

Annie petted the cubs.

“Don’t be afraid,” she told them. “You’ll get back to your mother.”

The big polar bear growled. She paced back and forth, sniffing the air.

Annie kept patting the two cubs and whispering to them.

Jack looked in the book for anything that might help. Finally he found something:

Even though a female polar bear can weigh as much as 750 pounds, she can walk on ice too thin to hold a person by balancing her weight and sliding her paws over the ice.

“Oh, man, that’s incredible,” whispered Jack.

He watched the mother polar bear walk down the snowbank.

On large silent feet, she crept about at the edge of the frozen sea.

She tried to step onto the ice. But each time she did, it cracked, and she had to retreat. At last, she found a firm spot.

Then the polar bear stretched out her four legs and lay on the ice. Slowly she moved forward, pushing herself with her claws.

“Is she coming for her babies?” said Jack. “Or is she coming to get us?”

“I don’t know,” said Annie. “Hey, let’s put on the masks.”

“What for?” said Jack.

“Maybe they’ll protect us,” said Annie. “Maybe she’ll think we’re polar bears, too.”

“Oh, brother,” said Jack.

But Annie gave him a bear mask. He took off his glasses and slipped it on.

Jack peered through the mask holes. It was hard to see the huge white bear sliding over the frozen sea. He squinted. That helped.

The polar bear looked at her cubs and let out a deep moan.

The two little bears carefully went to their mother. She licked the cubs and touched her nose against each of theirs. Then they crawled onto her back.

“They’re safe now,” said Jack. “Even if the mother breaks through the ice, she can swim with them to the shore.”

“Yeah, I just wish she wouldn’t leave us behind,” said Annie.

The mother bear slowly turned her body around. Then she pushed off with her hind legs. With her cubs on her back, she began sliding away.

“Let’s try moving like her,” Annie said.

“But we could break through and freeze to death,” said Jack.

“If we just stay here, we’ll freeze, too,” said Annie. “Remember, the seal hunter said his people had learned from the polar bears.”

Jack took a deep breath.

“Okay,” he said. “Let’s try it.”

He lay on his stomach. He spread out his arms and legs.

Then he copied the bear. He pressed his mittens against the ice and pushed off, sliding his feet.

Amazingly, there was no cracking sound.

“Grrr,” he growled. And he pushed off again.

Jack heard Annie sliding behind him. He kept going. He pushed and slid. He pushed again and slid again.

He made the movements over and over, until something happened: He didn’t feel like a boy anymore. He felt like a polar bear.

Then Jack felt something even stranger. He felt like a flying polar bear.

Jack swirled along as if his arms and legs were giant wings—and the moonlit sea ice were a glassy sky.

He remembered what the seal hunter had said: Polar bears can fly.