Act I
Harvey is a play about forty-seven-year-old Elwood P. Dowd, whose best friend is an invisible, six-foot-tall rabbit named Harvey. Dowd and his rabbit friend are well-known and liked in the taverns around town, but his relatives, who have come to live with him, are embarrassed by his behavior and try to have him committed to an insane asylum. The first scene opens with Dowd’s sister, Veta Louise Simmons, and her daughter, Myrtle Mae, throwing a luncheon for the older society matrons of the town. They count on Dowd being out, but he comes home suddenly, talking to Harvey and holding doors for him, and, worse, introducing him to the ladies at the party. As the party clears out, Veta swears that he will not disgrace the family again, and she asks him to wait in the den, which he does happily, while she goes to make arrangements for him to be committed.

Scene II takes place at the mental institution, Chumley’s Rest. Nurse Ruth Kelly, who is young and good-looking, interviews Veta about her brother, who is waiting outside in the taxi cab. When Elwood comes in, Kelly has an orderly take him upstairs. When the psychiatrist on duty, Dr. Sanderson, interviews Veta, he gets the impression that she is the one who has hallucinated Harvey (she admits to having seen him sometimes), and so he has her locked up. When he finds out that Elwood Dowd has been locked up, he assumes that a mistake has been made, and Dowd is brought down to the office, where Sanderson and Kelly apologize profusely, fearing that the sanitarium will be sued. Dowd, oblivious to the fact that he had been incarcerated in the first place, invites them both to have drinks with him later.

After Dowd leaves the scene (to explore the sanitarium where he has been told his sister is to be committed), Dr. Chumley, the esteemed director of the facility, enters and discovers that Dowd has left a hat with holes cut in the top. The hospital staff exits, then Dowd returns, just as Dr. Chumley’s wife, Betty, enters, and he tells her that he is looking for Harvey, explaining that Harvey is a pooka—a mythological spirit. After he leaves, she tells the others that he was looking for Harvey, and they realize that it was he, not Veta, who had delusions. They understand that the hat is Harvey’s, that the holes are for his rabbit ears. At the end of the scene, Wilson, the orderly, looks up ‘‘pooka’’ in the dictionary and reads out loud the definition that somehow, mysteriously, appears there: ‘‘A wise but mischievous creature. Very fond of rum-pots, crackpots, and how are you Mr. Wilson?’’

Act II
Scene I of Act II takes place in the library of the Dowd house. Myrtle is having the house appraised, planning to sell it as soon as Dowd is committed. Judge Gaffney has come to the house because he received a call from Veta, who was frantic. Veta arrives, distraught, telling of being handled roughly at the sanitarium when they tried to commit her, accusing the people who run the place of having unnatural interest in sex, and instructing the judge to sue them. Wilson and Dr. Chumley arrive from the sanitarium, looking for Dowd, with a list of bars and firehouses that they have been to in their search. When Judge Gaffney and Dr. Chumley leave together, discussing Veta’s impending lawsuit, Wilson and Myrtle flirt. They go off to the kitchen together, and Dowd comes in. He sees a flat parcel that Myrtle brought out of the garage to show Judge Gaffney, as evidence of David’s madness: a painting of himself and a large rabbit, in a polka-dot collar and red necktie. Putting the picture on the mantle, in front of his mother’s portrait, he leaves. Veta and Dr. Chumley enter, and he asks about the portrait over the fireplace and she, not looking, answers as if his questions were about her mother’s picture. Dowd phones, looking for Harvey, but while he is on the phone he says that Harvey just stepped in the door, so Veta determines that he is at a bar called Charlie’s.

Scene II of Act II takes place at the sanitarium again. Dr. Sanderson, having been fired for falsely committing Veta, is packing his belongings. He and Nurse Kelly discuss having seen each other out on dates the previous Saturday, indicating that they are jealous, although neither is willing to openly declare affection. Dowd enters and gives Kelly a bunch of flowers—Dr. Chumley’s prize dahlias. He is under the impression that Kelly and Dr. Sanderson are going to join him for a drink at a bar, and when Wilson enters, Dowd invites him, too. He tells them that he was out at the bar with Dr. Chumley earlier, that after a few drinks the doctor saw Harvey also. Near the end of this scene, Nurse Kelly asks Dowd about his life, and he explains in a long speech how he and Harvey make the acquaintance of strangers when they sit in bars:

Soon the faces of the other people turn toward mine and smile. They are saying: ‘‘We don’t know your name, Mister, but you’re a lovely fellow.’’ Harvey and I warm ourselves in these golden moments. We have entered as strangers—soon we have friends. They come over. They sit with us. They drink with us. They talk to us. They tell us about the big terrible things they have done. The big wonderful things they will do. Their hopes, their regrets, their loves, their hates. All very large because nobody ever brings anything small into a bar. Then I introduce them to Harvey. And he is bigger and grander than anything they offer me. When they leave, they leave impressed.

At the end of this scene, Dr. Chumley enters, nervously, as if someone is following him. He goes into his office and closes the door, and, soon after, the door opens and closes again, as if by itself.

Act III
Dr. Chumley, who was last seen locking himself in his office, is knocking at the sanitarium door; when Wilson answers, he explains that he slipped out of the window of his office and went around. He is terrified. Myrtle and Judge Gaffney arrive. She still wants Dowd committed, but the judge has evidence that there might actually be a Harvey. Reading from a note pad, he describes Veta’s testimony that she saw Harvey in her kitchen one morning, calling to her, and she chased him away by shouting, ‘‘To hell with you!’’ Myrtle says that Dowd, claiming Harvey’s help, is able to predict events in the future, such as the unexpected arrival of a neighbor’s aunt. Nurse Kelly and Dr. Sanderson arrive, behaving like a couple in love, and Dr. Chumley tells Sanderson that he isn’t fired after all. Sanderson suggests that Dowd should receive shock treatment with an injection of Doctor Chumley’s formula 977.

When Dowd arrives, Dr. Chumley asks to speak with him alone. They discuss Harvey’s power to stop time, which leads the doctor to fantasize about running off to a campground outside of Akron for two weeks with a strange girl who will stroke his head and say, ‘‘Poor thing! Oh, you poor, poor thing!’’ At Veta’s request, Dowd agrees to take an injection of formula 977, even though he would not be able to see Harvey any more. While he is in the next room for the injection, the cab driver who brought Veta comes in to collect his fare. She cannot find her change purse and so has to ask Dowd for money. The cab driver, noticing what a nice person Dowd is, remarks that he will not be so nice after the injection, that people he brings to the sanitarium always are nice until they are ‘‘cured.’’ Thinking about it, Veta realizes that she does not want Dowd changed, and she races in and stops the injection. Her change purse shows up before she leaves, and she realizes that Harvey had hidden it. The whole family leaves, with Elwood P. Dowd waiting a moment for Harvey to catch up with him.