Selina Kyle enters into the Gotham Zoo after-hours and examines a tiger kept in captivity. She calmly talks to the tiger, unaware of a sniper watching her from a tree. The sniper shoots her with a tranquilizer and jumps out at her. Selina insists that she won't let the man get to the tiger but her assailant tells her he's not there for the tiger. A security guard arrives and sees he sniper carrying off Selina and is horrified by his gorilla-like appearance. The guard is shoved into the tiger pit and the sniper runs off with Selina.
Meanwhile, Bruce Wayne waits for Selina outside a restaurant and gets worried as she's very late. He calls Alfred but Alfred knows nothing. Fortunately, an employee arrives and tells Bruce that Selina called and said she'd be late, as she would be visiting the zoo.
Believing Catwoman may be up to something, Bruce heads out to the zoo and hears the guard's story about the gorilla carrying Selina off and searches the premises. Finding the tranquilizer dart, he realizes something is wrong. Elsewhere, Selina wakes up and finds a large, humanoid cat-creature approaching. The creature closely observes and sniffs at Selina. Selina is worried but a man, Dr. Emile Dorian, arrives and introduces the creature as Tygrus and observes that he likes her. Dorian goes on to explain that he is a geneticist that works on creating new creatures such as Garth the ape man (Selina's assailant) and that Tygrus is the pinnacle of his work. He has now set his sights on Selina whom he knows is Catwoman. Selina thinks he's crazy but Dorian is unfazed and injects her with a serum.
Looking to get more clues, Batman goes to see Dr. Kirk Langstrom and asks about a compound he found in the dart. Langstrom identifies it as T-99: a compound used in splicing and the brainchild of his teacher, Dorian. Langstrom shows batman a cat/monkey hybrid and explains that Dorian likes cats better than he does people and has worked on combining cat DNA with other creatures. However, Dorian moved to an island when his work started bringing negative attention. Batman heads to the island and discovers a cat with bird wings flying around. Ignoring the cat, Batman seeks to break in through the skylight but Garth catches him. Batman and Garth crash into the skylight and Dorian tells Garth to leave them. Dorian then proudly shows Batman his newest creation: a new Catwoman. Batman is horrified but Dorian believes he's done Selina a favor. Batman attempts to free Selina and demands that Dorian reverse the project but Tygrus arrives and throws Batman from his father. Tygrus looks at Selina longingly but she looks away from him. Batman gets up and Tygrus, seeing him as a rival, attacks him. Batman is scratched and Selina runs up to Tygrus telling him to stop. Selina is confused as to what she is now and Batman tells her that he'll help her. However, Dorian orders Tygrus to take Batman outside and has Garth catch Selina in a net, much to Tygrus' displeasure. Dorian is intrigued by Selina's dominant human side and views Batman as a perfect chance to test Tygrus' abilities.
Batman is given a head start to escape from Tygrus and told that if he manages to beat the creature, he'll get the antidote to Selina's condition. However, Dorian lied about the head start and sets Tygrus out after him. Batman attempts to stop Tygrus with some gas bombs but this only serves to make him angry.
Inside, Garth and Dorian prepare to inject Selina with the final part of the serum but she refuses to allow it and escapes. Dorian is unconcerned as they are on an island and there is no way for Selina to escape.
Back outdoors, Batman and Tygrus struggle with one another and Batman finally manages to catch Tygrus in a net. Tygrus angrily shouts at Batman revealing that he can talk. He explains that Dorian told him that with Batman gone, Selina will love him. Batman tells him not to count on it and leaves.
With her newfound abilities Selina manages to track Batman who is crossing a rickety broken down suspension bridge. Unfortunately, Tygrus catches up with him and in the ensuing struggle the bridge. Unfortunately, Tygrus catches up with him and in the ensuing struggle the bridge breaks causing both combatants to fall. Fortunately, Batman manages to catch a tree growing from the cliff side and evades Tygrus who seemingly falls to his death. Selina finally manages to find Batman but before the two can speak, Tygrus arrives again. Selina gets in between them and tells Tygrus that Batman is not his enemy and her affections can't be won by killing him. Tygrus is confused, as his father told him the exact opposite of what Selina just told him, and he runs off.
Dorian is outraged that Batman is still alive and scolds Tygrus for his weakness. Batman arrives and says that he's not Tygrus' enemy and all he wants is the antidote and for Dorian to be brought to justice. Tygrus, however, can't leave his father unguarded and guards him. However, Dorian, blaming Selina for Tygrus' weakness prepares to kill her. Outraged, Tygrus stops him from shooting her and in a fit of anger Dorian threatens to kill him. This proves to be the wrong thing to say since Tygrus realizes his father has turned on him and goes on a rampage. Tygrus destroys the lab causing an explosion that topples the building. Selina is upset that Tygrus has died but Batman assures her they don't know that yet. Batman's assurance proves to be true as Tygrus emerges from the building carrying Dorian. Selina is now despaired as she is now stuck as a real Catwoman. Tygrus invites her to stay with him, but when Selina insists that she can't live like that, he sadly gives her the antidote and returns to the forests of the island. While Selina invites Tygrus to come with her, he turns her down and returns to the forest while Batman thinks back on Blake's poem "The Tyger."