While exploring Mars, Astronaut Jack Shindo encounters the alien lifeform Gudis battling Giant of Light, Ultraman Great. Jack is injured in the ensuing fray, but after defeating Gudis, Ultraman Great merges his mind and body with Jack and they return safely back to Earth. However, some of Gudis’ cells travel back to Earth and begin wreaking havoc, transforming all life they encounter into monsters! Jack and Great team up with the UMA defense force to protect the planet from Gudis’s evil influence.