On Christmas Eve, Miss Beadle decides to surprise the schoolchildren by letting them go home early. This proves to be a grave mistake when the kids are trapped by a vicious blizzard outside, and none of them can find their way home. As Doc Baker turns the school into a makeshift hospital for frostbitten victims, the men must brave the extreme weather conditions and track down their loved ones.

Doc Baker assists with an outbreak of mountain fever in a nearby town. The people of Walnut Grove are hopeful that the disease will pass their community by. Grace and Isaiah's young daughter, Alicia, becomes seriously ill, so Isaiah takes her to an abandoned house in town to nurse her back to health. Laura appears to have the fever as well, and Charles frantically sets out to find Doc Baker.