A space explorer, previously thought lost in space, returns to Earth and joins four teenagers in a search for a giant robot lion.

The Blue Lion delivers the team to an alien planet where they discover a mysterious castle. Inside, they awaken an alien princess who sends them on a mission to find the remaining lions.

The castle is attacked by an alien battle cruiser and the new Paladins must form Voltron.

As a Paladin threatens to leave the team, invaders get inside the castle and destroy its power crystal in hopes of stealing Voltron.