A blizzard moves into Chicago, stranding a family in the snow. Pratt, Abby, Hope and Ray must struggle to save the family, and keep hope alive when they learn one member is still missing. Luka's got a problem intern in his sights, and he's not pleased. Later, a gang shooting challenges Luka and Pratt. Meanwhile, Luka and Abby begin making wedding plans, but is their engagement still a secret? Sam makes a difficult choice about Alex, and wonders if she's failed him. Neela discovers she's no longer Dubenko's favorite, and Gates has an unexpected, and unwelcome, visitor.