Twelve-year-old Jack, his sister, and the family's foster child Troy go to Yellowstone National Park, where Jack's mother, a wildlife veterinarian, is investigating the report that wolves reintroduced to the park have killed a dog there.

"There are no polar bears left on Bear Island. At least, that's what April's father tells her when his scientific research takes them to a faraway Arctic outpost for six months. But one night, April catches a glimpse of something distinctly bear shaped loping across the horizon. A polar bear who shouldn't be there--who is hungry, lonely, and a long way from home. As their unlikely bond grows, April is determined to save her new friend--and so begins...