Up and coming rock band Greta van Fleet is heading back home from their last concert of the 2019 tour. They're exhausted, and expecting a good long break from the world before getting to work on the next album. Before they can even make it home, a celestial being appears and transports them to the war torn land of Thalassia where they are needed to save it from the grips of a selfish ruler. With the help of the native Thalassinians and their new found powers, Josh, Jake, Sam and Danny plunge themselves into the battle with one goal in mind - to kill the empress at all costs.