Convict Rex Shard is serving a life sentence at Megakat Maximum Security Prison and is forced to mine diamonds for Warden Cyrus Meece. While using a new type of diamond mining machine, the Gemkat 6000 – created by Dr. Lieter Greenbox (voiced by Robert Patrick), Shard tries to steal some of the diamonds collected in the machine. The machine explodes and crystals fuse to the left half of Shard’s body. Exiting the mine, Shard touches the prison guards watching over him and turns them into solid crystals. Shard realizes his new power and, after converting his entire body to crystal form, he goes on a rampage, seeking revenge against Warden Meece, Dr. Greenbox and anyone else who gets in his way by turning them into crystals. While doing a test run of new missiles in the desert, the SWAT Kats pick up a strange signal from the prison and go to investigate. It is up to them to put a stop the crystal menace and save Megakat City.