Batman and Robin sit perched on a rooftop watching for criminals. Nightwing arrives and has a quick conversation with his old mentor. While the two talk, Robin points out that someone is climbing to the top of a radio tower and stealing a circuit board.
Batman confronts the assailant but is attacked and thrown from the roof. While he is able to save himself with his grappling hook Nightwing and Robin are left to confront the criminal alone. Robin tries tying up the crook with bolas but the crook simply breaks the cords and takes off running. Nightwing gives chase and manages to knock off the criminal's hat revealing that it's actually a gorilla. Nightwing recognizes the gorilla as "Peaches," but she still manages to escape.
Later, Dick and Tim go to the circus where Dick grew up and check up on Peaches. Unlike the night before, Peaches is quite docile and friendly. The gorilla's trainer Miranda arrives and talks with Dick. Dick realizes that things have changed since he left the circus but learns nothing about the robbery.
That night, Dick looks through a photo album and reminisces about his past days. Batman arrives and explains that wherever the Haley Circus has been, there have been a series of robberies. Dick insists that Miranda had nothing to do with it but Batman is unconvinced, as it's been a long time since Dick had known her. Dick and Batman get a call from Robin and head out to stop another robbery. They arrive at the scene of the crime and discover a pair of bears sorting through some electronic devices. The bears take the offensive when the crime fighters arrive. Nightwing tries to slip one up bears with an oil barrel but the bear knows how to ride it. Nightwing realizes that these bears are from the circus. Batman and Nightwing manage to trap the bears under a car lift and behind a forklift.
The police return the bears, Polly and Dolly, to the circus. Like Peaches, they are now docile and obey Miranda without any trouble. Miranda insists that she knows nothing about how the bears managed to get out and what they were doing but Bullock doesn't believe her. He sets out to leave but runs into a clown that's resting on his car. This clown hassles him a bit and runs off.
Miranda heads back to her trailer and discovers Dick has gotten in. He reveals to her that the door was not locked. She insists that while she isn't very careful about her own door, she knows that the animal cages were locked. She believes that someone is messing with her animals and she intends to find out whom.
Dick returns to his apartment and finds that Batman is there waiting for him. He shows Dick a security tape of the bears actually knowing the access code to enter into a secure room. This reveals that the bears are too smart to have simply been trained.
Back at the circus, the clown that hassled Bullock approaches the bear cage and the bears walk up to the side of it. The clown reaches in and removes the control chips he implanted on the bears. Miranda arrives and confronts him and recognizes him as The Mad Hatter. Miranda prepares to attack but a boa constrictor wraps around her and traps her. Batman and Nightwing arrive at the circus and find Miranda trapped in the lion cage. They manage to save Miranda and she directs them to the big top. The Mad Hatter confronts Batman and Nightwing explaining that he learned how to control animals from a great distance but with humans he still needs proximity. At this point, Miranda turns on Nightwing and attacks him with her whip while the circus strong man grabs Batman. The rest of the circus performers arrive and start attacking the crime fighters. Fortunately, when the Fire Breather attacks Batman, Batman manages to trick him into setting the Mad Hatter's hat on fire getting him to remove it and setting the circus performers free.
Mad Hatter tries to escape and opens Peaches' cage in hopes of controlling her and having her help him to escape. However, Batman and Nightwing catch up to him and destroy his hat. Peaches then pins him to the ground and starts jumping on him.
Later, the circus is peaceful again. Dick explains to Bruce that Tim wanted to experience circus life so he arranged for him to live with Miranda for the rest of the week. Tim is greatly disappointed as his job is to clean up the cages. Dick, however, claims that he misses the life of show business.