The X's work for SUPERIOR, a covert agency sworn to defend Earth from evil. Mr. and Mrs. X have their daughter named Tuesday, their son named Truman, and many gadgets at their disposal. An organization called S.N.A.F.U. (short for Society of Nefarious and Felonious Undertakings) led by the evil Glowface is continually trying to cause trouble for the X's and other SUPERIOR agents through their plans to take over the world.