In a distant galaxy the world of Thundera is in crisis. The planet's structure has become unstable and is near collapse. With their destruction imminent Thundera's denizens--known as the Thundercats--escape in a spaceship and plot a course for a new home. While in transit the Thundercats are attacked by evil mutants and their craft is irreparably damaged. Jaga the eldest Thundercat sacrifices himself in order to pilot the ship safely to its destination: Third Earth.