The action of the play starts in Chamberlaynes’ London flat. Edward Chamberlayne is hosting a party, and Julia Shuttlethwaite, Celia Copletsone, Peter Quilpe, Alexander MacColgie Gibbs, and an unidentified guest are all in attendance. Alex has just told a story about a tiger, but no one seems to understand the story's significance. It is then Julia's turn to tell a story, and Celia encourages her to tell a story about "Lady Klootz and the wedding cake." Peter jumps on to fill in the other blanks: "And how the butler found her in the pantry, rinsing her mouth out with champagne."
Julia suggests that they all know it, but Celia asks the Unidentified Guest if he knows it and he says he hasn't. They get into a discussion about the fact that Julia is such a good mimic, but cannot remember if the character, Lady Klootz, is Lithuanian, Belgian, or Baltic. The Unidentified Guest does not know Lady Klootz, or Delia Verinder, the person from whom Julia first heard the story. They talk about one of Delia Verinder's brothers, "the only man [Julia] ever met who could hear the cry of bats." She tells them that the family had to find the Verinder brother an island where there were no bats.
As Edward leaves the room, Julia says that she will not tell the story until he returns, and they begin gossiping about him and the fact that he has been "quite impossible" since his wife Lavinia left before the party was thrown. It is in this moment that we learn that Edward is the host of the party, and has not supplied any snacks for his guests. Edward returns to the room and they continue chatting. Peter says he met a mutual acquaintance in California, while working on a film, but the film did not get produced.
Julia tells Edward to sit down and talks about the fact that this is her first opportunity to talk to him without Lavinia, something which she says Lavinia always wanted to encourage. "Lavinia takes me seriously," she says, "I believe that's the reason why she went away. So that I could make you talk. Perhaps she's in the pantry, listening to all we say!"
Edward insists she's not in the pantry, that she's gone to look after her ill aunt, her mother's reclusive sister, who lives in Essex. Julia asks for Lavinia's address in case she wants to drop by, then invites Edward to dine with her on Friday, alone. Abruptly, Julia says she has to leave, even though the other guests want her to tell the story of Lady Klootz. Suddenly, Julia does not know who Lady Klootz is. Alex says he has to go also, followed by Peter, and Celia.
Edward is left alone with the Unidentified Guest and insists that he stay. The Guest asks for gin with a drop of water, and Edward apologizes for the bad party, since it was made up of the only people he could find. Suddenly, the bell rings, and Julia comes back in for her umbrella. When she goes again, Edward asks the Guest's name, but he does not tell him. "The fact is, that Lavinia has left me," Edward tells him, adding, "Just when she's arranged a cocktail party. She'd gone when I came in, this afternoon."
The Guest asks for gin and tells Edward that he ought to also drink gin with water and sip it slowly while sitting down. Replying to the Guest's questioning, Edward tells him that he was married for five years, had no children, and knew of no affair. "If there's no other woman/And no other man, then the reason may be deeper/And you've ground for hope that she won't come back at all," the Guest says, to which Edward replies that he wants his wife back, resenting the Guest for using legal terminology that he himself uses in court and for being presumptuous about his situation.
"I know you as well as I know your wife/And I knew that all you wanted was the luxury/Of an intimate disclosure to a stranger," the Guest says, before telling him that telling a stranger anything "is to invite the unexpected." He makes a prediction that Edward's wife's absence will improve his life, and Edward tells him that he does not understand why she left, that it all felt "unfinished." The Guest waxes poetic about the nature of routine and the fact that people fall easily into their roles in marriage, before asking for more gin and water.
"To what does this lead?" Edward asks, and the Guest replies, "To finding out/What you really are. What you really feel." Edward worries about what he will do if his friends find out, but the Guest tells him that he must just forge ahead, and endure humiliation, as this will bring rewards. Edward is not so sure, saying, "I must find out who she is, to find out who I am./And what is the use of all your analysis/If I am to remain always lost in the dark?"
Suddenly, the Guest offers to bring Lavinia back, but only if Edward promises not to ask where she has been. As he tells Edward that Lavinia will come to him in 24 hours, the doorbell rings. It is Julia and Peter; Julia says she left her glasses there, and that one of the lenses is missing. As the Unidentified Guest leaves, Julia asks Edward who he is, but he does not know his name. When Julia finds her glasses, she leaves, but Peter stays behind to talk to Edward. He tells Edward that he had a difficult evening and that he thinks he and Celia have a lot in common, both being artists.
They discuss the fact that Celia is a poet, but Peter suggests that they share a love of film. They are suddenly interrupted by Alex, who has slipped in and wants to invite Edward out to dinner. When Edward says he does not want to go out to dinner, Alex offers to cook and rushes off to the kitchen. Edward and Peter discuss the fact that Peter met Celia at one of Lavinia's attempts at organizing a salon. Peter says that he met Celia a few days later at a concert. Alex interrupts them to ask whether there is any curry powder, clearly making some kind of Indian dish. When Alex leaves again, Peter tells Edward that Celia seems to have drifted away from him.
The play begins with a tableau of upper-class boredom and excess. A group of wealthy Londoners sit around telling stories they have already told before, none of them quite listening to the others. They swap languid witticisms, misunderstanding one story before begging another of them to tell one they already know. This opening scene is one that lightly satirizes the upper classes, paints them as uncreative and oblivious, unable to come up with anything enjoyable to do at a gathering, forced to rehash old stories, to which they do not even pay very close attention.
Another element of the scene that is illuminated here is just how little actual affection the characters feel for one another. As soon as Edward leaves the room, Julia begins gossiping about the fact that he has been different ever since his wife Lavinia left for a family emergency, and that this party, his responsibility, is not up to par. She complains that there is no food and that food is the only reason she would attend a cocktail party in the first place. "I can drink at home," she says, dismissively, suggesting that the only thing that has lured her to the party in the first place was the promise of food. By this logic, the characters do not enjoy one another's company; rather they are conforming to social custom and want to ostracize those who do not.
One of the more controversial plot points hanging over this first scene is the fact that Edward, the host of the party, was abandoned by his wife, Lavinia. For the beginning of the play, it is a piece of information that no one references, until Julia addresses it directly with Edward, suggesting that now, with Lavinia gone, there are so many private conversations they can have. Ironically enough, she is doing so not only immediately after having spoken behind his back, but in the presence of all the other party guests. In this moment, the audience begins to wonder about the exact nature of the public and the private realms, and what unusual standards govern this coterie of guests.
The whole atmosphere of the play is very mysterious and surreal. Characters know things one minute and forget them the next, they speak as though privately while surrounded by others, and they rehash the same old stories over and over again. Perhaps the most mysterious element of the play is the presence of the Unidentified Guest, whom no one can seem to identify. He remains nameless and acts as a sort of neutral sounding board for the other characters. When all of the other guests leave, he is still there, and Edward wants badly to talk to him, revealing to him the secret of his wife's disappearance. The Guest listens patiently, then offers his thoughts, at once completely presumptuous and completely unfounded, making it impossible to tell what he knows and what he does not. He tells Edward, "...let me tell you, that to approach the stranger/Is to invite the unexpected, release a new force,/Or let the genie out of the bottle." In this sense, the mysterious guest is afforded some kind of mystical role, that of "a new force."
The Guest turns quickly from a neutral listener into a peculiar kind of sage, a presumptuous advice-giver who schools Edward on how to rebuild his life and reclaim his identity in the wake of his wife's departure. He has a lot to say about the nature of custom, society, and marriage, and suggests that, though Edward is not admitting it yet, the absence of his wife will eventually help him reacquaint himself with his inner desires and his true self. He suggests that this suspension, the period of time in which Edward does not know what to do, will be important and that it is helpful to Edward's growth as a person. In this moment, the Guest turns into a kind of spiritual leader, a magical entity who predicts the future, encouraging Edward to embrace the unknown and his own feelings of "ridiculousness."