Avatar: The Last Airbender: North and South, Part 1 (North and South, #1)

When Aang leaves to aid Zuko with the Kemurikage, Katara and Sokka return to the Southern Water Tribe by themselves. Katara is shocked to find that her beloved village has become a bustling city, with none other than their father, Hakoda, in charge! A Northerner named Malina seems to be behind this change, pushing the North and South to be more unified…but what are her true goals?