The Subtopians have conquered Storm City and enslaved its citizens to work in their mine camps. In addition, Titanium Dax wants to have the stars of 2 Broke Girls found and hanged at dawn. Titanium Rex agreed to follow Dr. Devizo back to SuperMansion, despite not trusting him. When Subtopian soldiers attack, Rex and Devizo are saved by Robobot who brings them to the abandoned pizza restaurant where the League of Freedom and the Injustice Club are currently in hiding.
Rex is welcomed by everyone except her daughter Lex Lightning, who still resents him. Devizo enters and opens the suitcase with the Anti-Magno Rod and declares himself in charge of the truce. Rex reveals that Subtopian technology is powered by Magno, which becomes Anti-Magno upon being depleted of its energy, becoming lethal to Subtopians. Rex and Devizo come up with a plan to invade the Subtopian controlled military base for the atmospheric dispersal device needed to spread the Anti-Magno's energies. After both sides get the ordered meats from Arby's manager Deandre, Titanium Rex and Lex Lightning fly to the military base.
As Black Saturn, Ringler, Cooch, Buster Nut, and Groaner plan a diversion attack on the Anti-Magno storage facility, Robobot, Blue Menace, Johnny Rabdo, Robo-Dino, and Chet's evolved form are the full-frontal assault. American Ranger and Portia are visited by Sgt. Agony who takes control of the operation as he outranks Ranger. Dr. Devizo prepares the adapter for the atmospheric dispersal device which gets a setback when Blazar's monkey form urinates on it.
A flashback shows that Frau Mantis had Dr. Devizo raise Lex Lightning. Robobot leads his group into the full-frontal assault. As Devizo has suspended accounts from Uber and Lyft, Deandre gives him a ride to the military base. During Rex and Lex's fight with the Subtopian soldiers, Dax arrives where he is surprised that Lex is the result of Rex mating with a "dirt walker" and declares that she must die. Rex tells Lex to leave so he can fend off Dax, but she returns to save Rex from dying at the hands of Dax. Lex takes a beating from Dax before she uses her titanium hand to defeat him. After Dr. Devizo attaches the adapter to the atmospheric dispersal device, Rex flies it high above Storm City. Dr. Devizo arranges for Rex to "die a hero" by detonating the device when he isn't out of range.
As the Subtopians retreat, Lex flies into the cloud and catches Rex. Dr. Devizo then carries Titanium Rex's body, taking credit for thwarting the invasion and saving Titanium Rex's life. As a result, Dr. Devizo is pardoned for all of his crimes. Portia gets back together with Ringler and they take their leave much to the dismay of American Ranger and Sgt. Agony and the disappointment of Black Saturn.
As Rex is recuperating, he agrees to testify at Lex's eventual criminal trial and offers her a place in the League. Lex states that Lex Lighting "retired" and is now calling herself Titanium Lex. Sgt. Agony then appears on TV stating how villains are misunderstood people and states that he has hired Dr. Devizo to help him oversee the future conduct of the League of Freedom. Dr. Devizo then states that he is looking forward to working with Titanum Rex again much to Rex's dismay.
