The play is set in the Norway of the 1880s. As Act 1 begins, festive tables are laid in the office of a wealthy Norwegian businessman Werle. Old Ekdal, a dejected and decrepit man, sneaks in through a back way; seemingly, he has business with Werle but does not want to be seen at the party. Meanwhile, at the party, Old Ekdal's son, Hialmar Ekdal, is in attendance as a guest of Werle's son, Gregers Werle. The two have not seen each other for 15 years. Within this time, Hialmar married a woman named Gina, had a daughter named Hedvig (she is now fourteen), and started his own business—a photographer’s studio. Also within this time, Hialmar was unable to finish his studies at the university due to public shame and lack of funds: it seems his father, the former business companion of Werle, was put in jail after betraying Werle and conducting shady business. Even so, Werle decided to be charitable towards Hialmar: he gave Hialmar the money for his studio equipment, as well as the money to learn the craft of photography. This all seems suspicious to Gregers, who knows his father very well and suspects that Werle had an ulterior motive in doing so. Gregers' suspicions are only confirmed then, when he learns that the maiden name of Hialmar's wife is Hansen. Suddenly, after being locked in Werle's office, Old Ekdal and Gråberg (Werle's bookkeeper) exit right through the middle of the party, much to everyone's shock and to Hialmar's embarrassment. Hialmar even claims that he does not recognize his own father. The party settles, Hialmar leaves, and Gregers has a word with his father in private while Mrs. Sörby, the housekeeper, entertains the guests. In his conversation with Werle, Gregers then uncovers and reveals some shocking facts: first, Gina Hansen used to be a former mistress of Werle's while Gregers' mother was on her deathbed; second, it seems that Werle was really the one who betrayed Ekdal, and not the other way around; third, it seems that Werle has been helping the Ekdals in order to tie up loose ends and avoid feelings of guilt. Werle also tells his son that he intends to marry Mrs. Sörby and move to the Höidal works, where Gergers had been working, but Gregers refuses to play the part of the filial son. Then, firmly rejecting the Werle’s proposal to become his companion in business and in supporting his marriage, Gregers announces that he is severing ties with him. He claims that he now has a special mission in life, and he leaves.
Act 2 opens at the apartment of the Ekdals. Upon returning home, Hialmar is greeted by Gina and Hedvig, who ask him a great deal of questions about the fancy dinner he just attended. It is clear that, though the Ekdals do well enough to support themselves, they are generally without luxuries: Hialmar's evening coat was borrowed, only bread and butter is available in the house, and Hialmar has brought the menu of the dinner as a gift for Hedvig, so that she can experience the luxuries of the dishes vicariously through his descriptions. Old Ekdal, meanwhile, is getting drunk in his room, but emerges to comment on a yet unknown project with Hialmar, taking place in the garret of their apartment. The family settles and is about to enjoy some flute music provided by Hialmar, but someone arrives at the door—Gregers Werle. Gregers says that he has left his father's home and is staying in a hotel, but Hialmar soon suggests that Gregers rent the empty room in their apartments. Hialmar then acquaints Gregers with his family, introducing him to Hedvig and indicating that, like Werle himself, Hedvig suffers from a hereditary disease that causes encroaching blindness. Old Ekdal comes out drunk, dressed in his former military cap, and discusses hunting with Gregers. When Gregers implies that there is not much opportunity for Ekdal to hunt anymore, Ekdal rebuts him by showing him exactly what is in the garret: a full hunting ground, complete with a variety of animals. Prized most among them is a wild duck, gifted to them by Werle after he injured it on a hunting trip. When his shot failed to kill the duck, it attempted to dive to the bottom of the lake and die, but Werle's hunting dog saved it. This story has a profound effect on Gregers, who sees it as a symbolic parallel to the story of how his father bother ruined and saved the Ekdal family. It soon becomes clear what Greger's mission is: he wants to open Hialmar's eyes to the quagmire of lies into which he has been plunged by Werle. Gregers sees Hialmar as a naive but great soul, and he strongly believes in his goodness. Though Gina resists, Hialmar ultimately rents Gregers the room, and he decides that he will move in the following day. He is also told of the downstairs neighbors, a drunk named Molvik and a dastardly doctor named Relling.
Act 3 takes place the following day. Gregers has moved in and made a big mess in his rooms while attempting to light the stove. Hialmar is supposed to retouch photos for his business (for which Gina also coincidentally keeps books and retouches), but he allows Hedvig to take this on while he assists his father in the garret with work for the wild duck. While Gina is preparing a lunchtime meal, Gregers comes in and talks with Hedvig. He learns from her that the garret used to belong to a sailor called "The Flying Dutchman," who has since died and left a treasure trove of books and curios in the garret, each of which fascinates Hedvig. She believes that, in the garret, time seems to stand still. Gregers engages Hedvig in conversation, and he seems to take advantage of her curiosity to make her question the reality of things (for example, asking her if she is sure that the garret is merely a garret, and nothing else). Shots then ring out in the garret, surprising Gregers. Hialmar emerges with a pistol, however, and tells Gregers that they are able to hunt and shoot in the garret without others hearing, making it a perfect diversion for Old Ekdal. In a private conversation, Hialmar tells Gregers that the pistol was once owned by Old Ekdal, who almost used it to commit suicide after his public downfall and shame. Later, Hialmar says, he himself almost used it to commit suicide rather than cope with the public shame of his family's humiliation. What saved him, Hialmar explains, was his family, for whom he also hopes to make an invention that will allow them to live easily and not worry about money. Lunch then takes place, with Molvik and Relling coming up to join as guests. Relling, who knew Gregers at the Höidal works, centers the discussion on how destructive of a presence Gregers was in the past, hurting others in his pursuit of the "claim of the ideal" (48). Relling presses Gregers on what he takes to be unfounded and irrational idealism, but this only gets Gregers talking in rather dark and desperate terms about the Ekdal family situation, saying that they are subject to poison marsh vapors (again evoking the image of the duck drowning in the marsh after being shot). Suddenly, just as the conversation reaches a heated point, Werle himself comes to the door. Here, Gregers explicitly reveals his plan of opening Hialmar's eyes to his father, and he once again rebuffs his propositions. We also learn here that Werle was to gain a sizable dowry from Gregers' mother, though this never actually came to pass. As Act 3 closes, Gregers takes Ekdal out on a long walk (i.e., to tell him the truth), and Relling meanwhile tells Gina that Gregers has gone mad with "an acute attack of integrity" (53).
As Act 4 opens, Hialmar is just returning from his revelatory walk with Gregers. Upon entering, Hiamlar announces that, from now on, all studio affairs and home accounts are to be conducted himself: he no longer trusts Gina. Hialmar pressures Gina to confess about her intimacies with Werle, and while Gina does not deny a past relationship, she asserts that what happened between them happened only after the death of Gregers' mother, when Gina was no longer working with Werle. Gina tries to calm Hialmar down and reason with him, which he does slightly, but just then, Gregers enters and attempts to press Hialmar to stay true to the ideals of truth, openness, and transparency. Just then, Relling enters too. He learns of what Gregers has done, then verbally attacks Gregers for the unreality of his ideals, saying that no ideal or perfect marriage can exist in this world. At the same time, someone comes to the door. It is Mrs. Sörby, who has come to bid Gina farewell. She admits her intent to marry Werle and care for him, and she mentions that their trip to the Höidal works is partially fueled by Werle's encroaching blindness. Hialmar initially takes this as karmic retribution for his betrayal of the Ekdal family. Mrs. Sörby leaves. Just afterwards, Hedvig enters from the hall, saying that Mrs. Sörby has given her a gift for her birthday the following day, but that she is not meant to open it until then. Hialmar is upset about being kept in the dark once again, so they open the letter at once. It is a deed of gift, granting Old Ekdal a generous allowance of 100 crowns a month from Werle's office, and then passing this gift on to Hedvig for the entirety of her life. This, combined with the news of Werle's eye disease, convinces Hialmar that Hedvig is not his daughter after all, but Werle's. Hialmar tears up the deed of gift, and Hedvig runs off. This whole realization pushes Hialmar to the breaking point, something that is only worsened when Gina honestly cannot say for sure who Hedvig's father is. Hialmar vows never to return to their apartment, and leaves, tearing Hedvig off of him when she tries to stop him. Once again, then, Gregers has a moment with Hedvig in which he is able to manipulate her with his ideal philosophies. He tells her that, in order to convince her father that she loves him, she has to kill the wild duck, or else have her grandfather kill it for her. Gregers, Gina, and Hedvig then part, waiting to see how Hialmar returns the next day.
At the start of Act 5, Gina and Hedvig are wondering where Hialmar went the previous night, and they suspect that he went out with Relling and Molvik. Relling then arrives, confirming that Hialmar was with them the previous night. While Gina and Hedvig go into the sitting room, Relling and Gregers then discuss why Hialmar has been so troubled by this series of revelations. Gregers says that Hialmar should be liberated with the revelation of truth, having a simple mind, but Relling says that Hialmar is a far more complex man than this, having excelled at university. He also tells Gregers that everyone must have a "life-illusion" of purpose, regardless of how false it is, to avoid falling into desperation (75). This is why Relling pushed Hialmar to start work on an invention—in order to blissfully occupy him and to solidify the illusion of his stable family life after the earlier catastrophe involving Old Ekdal. Meanwhile, Hedvig attempts to get Old Ekdal to shoot the wild duck for her, but he refuses. She takes the pistol earlier used by her father and goes into the garret to kill the duck herself. Hialmar then enters, preparing to pack his things and leave Gina forever. She gently coaxes him down from this extreme, though he is still mad and intends to leave her and Hedvig in a slower fashion. He also states his intent to repair the deed of gift so that their family can be provided for more easily. Gregers then comes in again, telling Hialmar that he need not leave, since Hedvig has resolved to have the wild duck, the living symbol of Werle's original treachery, killed in order to show her love for her father (she treasures the duck, so her willingness to sacrifice it shows that she really does value Hialmar above everything). Suddenly, a shot is heard in the garret. Gregers rejoices, thinking that Old Ekdal has ended the family's misery. Old Ekdal, however, enters the room from the other side, dressed in his full military uniform. When they go to investigate the garret, then they find that Hedvig has accidentally shot herself. Tragedy abounds, and Gina and Hialmar are reconciled at last over Hedvig's death. Dr. Relling, however, does not think that Hedvig died by accident: since her dress is scorched from the gunpowder, he believes that she deliberately shot herself. Relling blames Gregers for her death because of his manipulation and imposition of his extreme idealism on the family. Gregers only answers that he is going towards his destiny, to be "the thirteenth at table" (implying either Jesus or Judas at the Last Supper), and Relling closes the play by calling him a devil.
