Thirteen-year-old Helen is not entirely sure she is looking forward to spending the next six months on board the Karluk, a ship headed on an Arctic expedition. But with the recent death of her father, it is the only work her seamstress mother can find. Helen's nine year-old brother, Michael, is delighted to be off on a real adventure but neither he nor Helen could have realized just how extraordinary this trip would be. The ship's hard-bitten captain, Robert Bartlett, must use all his seafaring skill when the Arctic Ocean begins an early freeze-over and the ship becomes trapped in ice. But will Bartlett's knowledge of the unpredictable and treacherous Arctic be enough to save his passengers?