The play is set in the small town of Mesalia, Ohio in the weeks leading to Christmas in the 1930s. The exposition reveals that the famously outlandish radio wit Sheridan Whiteside of New York City was invited to dine at the house of rich factory owner Ernest W. Stanley and his family. However, before Whiteside enters the house, he slips on a patch of ice outside the front door and injures his hip. He is attended by Dr. Bradley, the absent-minded town physician, and Miss Preen, his frantic nurse.
Whiteside meets the eerie Harriet Stanley, Mr. Stanley's sister. She presents him a holly branch as a present. Whiteside, though taken aback by her bizarre nature, is convinced that he has seen her before. Whiteside then meets young newspaper editor Bert Jefferson. Whiteside, initially disdainful of the newspaperman, soon respects Bert's brave charm and permits an interview. Whiteside explains that he cannot wait to leave Mesalia, and that he is a paid authority on famous murders.
Whiteside, after fuming over Maggie's planned departure, skims over Bert's play. He then contacts Lorraine Sheldon, his famous actress friend with a sleazy reputation, to visit Mesalia to convince Bert to give her the part in his play through any means necessary. Lorraine agrees.
Meanwhile, Dr. Bradley returns with the news that he confused Mr. Whiteside's X-Ray with old Mrs. Moffett's X-Rays, and that Mr. Whiteside isn't actually hurt at all. Dr. Bradley declares that Whiteside can leave the Stanley's home immediately. Whiteside, attached to his scheme to separate Maggie and Bert, convinces Dr. Bradley to conceal the "good news." In return, Whiteside promises to help edit Dr. Bradley's lengthy memoir, "Forty Years an Ohio Doctor."
Richard walks in, informing Whiteside that he wants to be a photographer, against his father's wishes. Whiteside says that Richard should do it. June enters and presents her boyfriend, Sandy, a labor-organizer in Mr. Stanley's factory, to Whiteside, informing him that they wish to get married. Whiteside advises them to get married that very night. Sandy quickly leaves, and June runs upstairs.
Lorraine Sheldon arrives and chitchats with Whiteside over gossip as well as the plan to seduce Bert. Maggie and Bert enter and Lorraine immediately starts flirting with Bert. Bert offers Lorraine a ride to her hotel, and they depart together. Maggie suspects Whiteside's involvement. She prepares to confront him when Beverly Carlton walks in. After delighting Whiteside and Maggie with an impersonation of Lorraine's latest fling, the English aristocrat Lord Bottomley, Beverly plays a song on the piano, his own composition entitled "What Am I To Do?" After the song, Maggie wheels Whiteside into the library, seizing a moment with Beverly. Maggie informs Beverly of the situation involving Bert, Lorraine and Whiteside. Beverly offers to help, and Maggie whispers a plan into Beverly's ear. Beverly accepts the challenge and leaves.
After radio men arrive to prepare for Whiteside's broadcast, June and Richard leave with their luggage. Lorraine enters and the telephone rings; it is a trans-Atlantic call from Lord Bottomley. Over the phone, Lorraine accepts Lord Bottomley's marriage proposal. Bert arrives and informs the group that he got a two-minute interview with Beverly Carlton at the train station, but Beverly stood in a phone booth most of the time, "making....faces for about five minutes." Bert leaves the room to prepare cocktails. Whiteside realizes that Beverly mimicked Lord Bottomley at the behest of Maggie, proving this to Lorraine with the records from the telephone operator. Lorraine, embarrassed, cancels her plans. After realizing it was Maggie's fault, Lorraine vows to break up her relationship with Bert.
The radio men enter the living room to set up equipment. Bert enters and Lorraine informs him that she is staying, and wants to read his play. Maggie storms out; Bert follows her. Mr. and Mrs. Stanley enter and walk upstairs as choir children are ushered into the home, but quickly rush back down with letters from their departed children. The letters inform them that Whiteside recommended their decisions. Whiteside attempts to read his Christmas address with the backing of the choir singing "Silent Night," but is interrupted when Miss Preen bursts out of the library after a penguin bites her. The penguin follows and panic ensues.
Harriet Stanley enters to watch Whiteside open her present to him, an old photograph of Harriet taken in her twenties. Whiteside is still convinced that he has seen her face before. The doorbell rings; it is the zany Banjo, Whiteside's Hollywood comedian friend. Banjo fondles Miss Preen, who quickly runs into the library. Whiteside informs Banjo of the situation involving Maggie, Lorraine and Bert. He feels guilty, and wants to make it up to Maggie by getting Lorraine out of town. The pair are unable to come up with a realistic plan. Miss Preen exits the library, carrying her luggage. She informs Whiteside that she is so disgusted with him that she is walking out on this case as well as the nursing profession, and leaves.
Mr. Stanley enters with June, having found her before she got married; Richard has been apprehended in Toledo and is being brought back home. Mr. Stanley invites two deputy sheriffs into the home, who tell Whiteside they have a warrant to forcibly eject him from the Stanley residence if Whiteside does not leave within fifteen minutes. Richard is brought in by a detective, and Mr. Stanley informs Whiteside that he has ten minutes remaining.
Lorraine enters, explaining that she loves Bert's play and that she is deliriously happy with Whiteside. She sets her muff on the sofa and sits down. Banjo enters; an uncomfortable moment passes as Lorraine detests Banjo for publicly embarrassing her some years back. Things become even more uncomfortable when Maggie enters looking for a copy of the New Year's Eve broadcast. Lorraine mentions to Maggie that she will be hearing the broadcast in Lake Placid with Bert. Maggie exits.
The moving men bring a mummy case into the living room. It is a Christmas present to Whiteside from the Khedive of Egypt. Whiteside begins to show desperation as Mr. Stanley announces the five minute mark. Lorraine, taken with the case, opens it, stands inside, and recites a few lines of poetic dialogue. Whiteside gestures to Banjo to close the case and trap her inside. Maggie briefly re-enters the room, handing Whiteside the photograph he received from Harriet. After taking another look at the picture, Whiteside informs Banjo that he recognizes Harriet, and knows how to get Lorraine and the mummy case out of the house.
Mr. Stanley enters, telling Whiteside the time is up. Whiteside asks for a favor from Mr. Stanley: to have the sheriffs help Banjo take the mummy case to the airport. Mr. Stanley refuses, whereupon Whiteside stands up and confronts Mr. Stanley. Whiteside reveals that Mr. Stanley's sister is the infamous Harriet Sedley, who murdered her mother and father with an axe twenty-five years prior in Gloucester, Massachusetts. Whiteside will inform his radio audience of Mr. Stanley's sheltering of his murderous sister unless Mr. Stanley does what Whiteside has requested. Mr. Stanley grudgingly complies.
Maggie enters, and Whiteside hands her Lorraine's muff as a "Christmas gift". Maggie realizes what Whiteside has done, and is surprised and touched by Whiteside's compassion. Whiteside takes Maggie's train ticket so that he can return to New York as quickly as possible, leaving Maggie to pursue her romance with Bert. Bert enters, and Whiteside gives him some intimidating parting words. Whiteside also tells Bert that he (Whiteside) will be sending Bert's play to Katharine Cornell. Whiteside lastly tells Mr. Stanley "good-bye," along with a request that Mr. Stanley allow June and Richard to follow their dreams, "or else". Maggie and Bert embrace, and Mrs. Stanley descends the stairs as Whiteside is heard slipping and screaming from outside. Dr. Bradley and Bert carry Whiteside back into his wheelchair. Whiteside exclaims that he is going to sue Mr. Stanley for $350,000, and the play ends.
Woollcott was delighted with the play and was offered the role for its Broadway debut. With his busy schedule of radio broadcasts and lectures he declined and Monty Woolley played the part. Woollcott did play Whiteside in the West Coast version of the play, and was even joined by Harpo Marx, who portrayed his own referenced character, Banjo.
The printed edition of the play starts with the inscription "To Alexander Woollcott, for reasons that are nobody's business."
Banjo was modeled after Harpo Marx, and there is a dialogue reference to Marx's brothers Groucho and Chico. When Sheridan Whiteside talks to Banjo on the phone, he asks him, "How are Wackko and Sloppo?"
The song "What Am I To Do" was written by Cole Porter specifically for the play.
Harriet Stanley, the alias for Harriet Sedley, is an obvious reference to the famed Massachusetts murderer Lizzie Borden. The popular jump-rope rhyme referencing Borden, with her name replaced with that of Harriet Sedley, is repeated in the play.
A 2000 revival, which ran for 85 performances, was produced by the Roundabout Theatre Company and directed by Jerry Zaks. The cast included Nathan Lane (Sheridan Whiteside), Jean Smart (Lorraine Sheldon), Harriet Sansom Harris (Maggie Cutler), and Lewis J. Stadlen (Banjo). In an interview prior to the opening, Lane said, "There's a danger in playing Whiteside. In the movie, Monty Woolley's portrayal at times came across as mean for mean's sake. It's when it gets nasty or bitchy that it goes off in the wrong direction." He suggested that his performance was influenced by Woollcott's repressed sexuality, stating, "He had a lot of...things he didn't want to deal with."
The 2000 production received mixed reviews. Variety, The Advocate and Talkin' Broadway reviewed it positively, and Entertainment Weekly gave the production a B+, calling it "as fresh a send-up as an SNL sketch and [with] an even more inspired plot" and singling out Smart's "swanning demonstration of ultimate showbiz phoniness" for praise. In The New York Times, however, Ben Brantley disliked the production, writing that "What should be a buoyant balloon of an evening [is] more often an exercise in deflation." Brantley praised Stadlen but found most of the acting, including Lane's, to be "a series of flourishes that sell individual jokes and epigrams without being anchored to character. Smart was nominated for the Tony Award for Best Actress in a Play and Stadlen was nominated for the Drama Desk Award for Outstanding Featured Actor in a Play, though neither won. The production was broadcast by PBS on October 7, 2000, three days after the New York production closed, and was released on DVD.