Carol Carlisle, the daughter of the Secretary General, is testing her invention she calls the ""Agra Ray."" The radiation from the device enables plants to reach full maturity within a number of hours. However, the ray may be perverted into a powerful weapon with the capability of turning entire cities into stone. Unknown to Ms Carlisle, her assistant is agent of Prince Greegor of Mercury. The lab assistant steals the Agra Ray and kidnaps Ms Carlisle, transporting them to Mercury, where Prince Greegor plans to threaten Terra, the Capitol of the United Planets.