Christopher Fielding has no choice but to spend Christmas with his family in York, away from William Macpherson, the biology professor with whom he has fallen in love. Finding his sister Nan in some distress over her pregnancy, Christopher makes a wish that all will be well with her and the baby, and another that William, traveling by train to his family in Scotland will be safe from the blizzard raging over the countryside.
As Christmas Eve approaches, William's train is stranded in snow drifts and Nan's baby is about to arrive prematurely. Cut off by the weather from a doctor's help, the family is in despair, and Christopher feels that his wishes may not be enough. Perhaps what they now need is nothing short of a miracle.