Chairman Hawkman tells the JSA that all cases in the works are closed and, with nothing for them to do, Green Lantern suggests that all attend the circus, which has just come to town. As they near the circus, a Policeman tells them the Police Chief needs to see them, and the Chief informs them that he expects a major crime wave to strike Civic City within the week. Four cities have already been hit, each at 9pm in the evening, and each having had a traveling circus in town. This fact leads the Flash to suspect the circus in town is somehow responsible and all decide to investigate.; Hawkman boards an ocean liner to protect "The Pharoah", a valuable oil painting, but discovers Felix the Great and two circus clowns have already seized the painting. The Winged Wonder foils the robbery and jails the suspects, but is stunned to discover that Felix is performing at the circus! Likewise, the Flash and the Atom set out to guard Mrs. Rockmillion's prize Pompeii Tiara, but Frederick and his trained elephants purloin the tiara. The All-Stars stop the crime and jail the felon, but when the two return to the circus, they are shocked to see Frederick performing his routine!; At the Great Museum of Natural History, Dr. Mid-Nite and Wonder Woman are there to protect an expensive collection of electrum coins, but have to battle Demon Dan. who has seized them. They round him up and jail him, but then discover him at the circus performing! Meanwhile, G.L. arrives to the estate of Alvin Marcey to guard his Harmonimac (automatic orchestra) in time to foil Mr. Mechanico and Goliath from stealing it. Having jailed the pair, the Green Gladiator returns to the circus too see the pair in mid-performance. Both he and Black Canary wonder what is going on.; With all the JSA members re-assembled at ringside, they are stunned to see every one of the people that they had thrown into jail for committing crimes in the center ring! At that moment, Alimand announces to the crowd that the JSA will perform some feats, which they do....and the villains take it on the lam. The All-Stars round up the crooks, take them to the Police Station, where they are amazed to see two sets of circus performers. Finally, Alimand confesses that the Circus of a Thousand Thrills is, perhaps, the rarest circus of them all, because they have identical twin performers!