As Frog Princess is crowned Frog Queen, the neighbouring Kingdom of Moles faces an existential threat when it is flooded by polluted water. Evil scientist Dr. Mole persuades Mole King that the water originates from Frog Kingdom, prompting a declaration of war on its neighbour. Despite her soldiers' brave resistance, the young and inexperienced Frog Queen loses the first battle.
Frog Queen is rescued by Master Groundhog who teaches her the importance of unity and wisdom for a leader in times of both war and peace. When she eventually returns to Frog Kingdom, Frog Queen rouses her troops to win a final victory over the moles. The Mole King accepts her peace treaty. But Dr. Mole has his own plans, harnessing an army of crazy frogs that have emerged from the polluted waters to force a combined kingdom under his rule.
With the help of Master Groundhog, Frog Queen leads her troops to vanquish Dr. Mole, foiling his environmentally catastrophic plot. Frog Kingdom and Mole Kingdom enter a new era of peace.