Peter, a successful upper-middle-class man who works in the publishing business, is reading on a bench in Central Park in New York City on a sunny summer afternoon. Another man, Jerry, an aimless, rootless outsider who describes himself as a “permanent transient,” declares that he has come from the zoo and insists on talking to Peter. Peter does not want to be bothered. He tries to brush off Jerry and get on with his reading, but Jerry confronts him to examine his life. In the course of their conversation, the audience discovers that Peter is married; has two daughters, two parakeets, and two television sets; lives in a nice neighborhood; and has an executive position in textbook publishing. When Peter questions Jerry about his life, Jerry accuses him of trying to make sense out of things and bring order to a chaotic world. Although these two men are nearly the same age, one in his late thirties and the other in his early forties, they seem to have very little in common, at least on the surface.

Jerry tells Peter that he has had only short-term relationships with women. After discussing the difference between fantasy and reality, Jerry abruptly brings the conversation back to the reason for his trip to the zoo. He proceeds to tell Peter a long, detailed story about his landlady and her dog, who are the gatekeepers of his dwelling. Jerry lives in a rooming house, and the landlady’s dog attacks him every time he comes in. He is fascinated with and challenged by the dog’s hatred and wants to find a way to make contact with the animal. He tells Peter that he decided that he would first try to kill the dog with kindness, and if that did not work, he would simply kill it. He fed the dog hamburgers, but the dog’s hatred did not diminish. He then decided to give the dog a poisoned hamburger, but still nothing happened. The dog did not die, nor did it come to love Jerry. For a brief moment, Jerry and the dog looked at each other, but then the dog withdrew from contact with him. Even its hatred seemed gone forever.

Not able to make contact with people, Jerry had tried to make contact with a dog, but even this had failed and proved nothing. Now, whenever he and the dog meet, Jerry tells Peter, they regard each other “with a mixture of sadness and suspicion, and then we feign indifference.” An “understanding” has been reached: The dog no longer rushes Jerry, and Jerry no longer feeds or poisons the dog. Jerry then announces, “The Story of Jerry and the Dog, the end,” bringing to an effective and dramatic close the important second part of the play.

Upon hearing this story, Peter shouts that he does not understand and does not want to hear any more. Jerry tells Peter that he will explain what happened to him at the zoo, but first he must explain the reason for his visit. Jerry went to the zoo to find out about the way people exist with animals and the way animals exist with one another and with people. After telling Peter that in the zoo everyone is separated from everyone else, Jerry begins to punch Peter and move him off the park bench.

Jerry tells Peter that he is crazy and wants the bench on which Peter is sitting. Peter screams furiously for the police and yells at Jerry to get away from his bench. Jerry says that he needs the bench, calls Peter a vegetable, and prods him to defend the bench. They begin to fight for the bench. Jerry takes out a knife and throws it at Peter’s feet. Peter picks up the knife to defend himself. Jerry then charges Peter and impales himself on the knife. Although Jerry is dying, he thanks Peter for not going away and leaving him, and for giving him comfort. With his dying breath, Jerry tells Peter that he has been dispossessed, as he has lost his bench, but he has defended his honor. Jerry has made contact with another human being, even if it has cost him his life. Jerry says that Peter is really not a vegetable but an animal. The entire human condition for Jerry is a zoo story of people (and animals) forever separated by bars. The play ends with Peter howling, “OH MY GOD!” as he leaves Jerry, who is uttering the exact same words, to die.