Despite the Dornish staying away from most affairs within the Seven Kingdoms, Prince Oberyn Martell and his lover/paramour, Ellaria Sand, have traveled north from Dorne to the capital of King’s Landing, as King Joffrey Baratheon’s wedding is days away. On the outskirts of the city, the king’s uncle, Tyrion Lannister, is sent to welcome Oberyn’s older brother, Prince Doran Martell, to the capital, the leader of House Martell. However, Tyrion is informed by a Dornish bannerman named Lord Blackmont that Prince Doran's declining health prevents him from leaving the Dornish capital of Sunspear, and therefore he has sent his brother Oberyn to attend the wedding in his stead. Blackmont also informs that Oberyn went ahead and entered the city before dawn. Assigning the reception of the Dornish lords to the City Watch, Tyrion informs the sellsword Bronn that they should find Oberyn as soon as possible "before he kills somebody or several somebodies." Along the Street of Silk in King’s Landing, Prince Oberyn and his lover Ellaria are examining prostitutes in Lord Petyr Baelish’s brothel, currently managed by Olyvar. When Olyvar calls Ellaria "my lady," she calls him out for using a lie to address her and tells him to call her what she is: a bastard. The Dornish couple choose a contortionist named Marei, and Oberyn then orders Olyvar himself to get undressed also, revealing a sexual fluidity that is common with Dornish people. Their escapades are interrupted, however, when Oberyn overhears men singing the infamous House Lannister victory song "The Rains of Castamere" in the next room. Ellaria tries to stop him but can only watch as Oberyn takes out his rage on the Lannister men-at-arms, who insult him and Ellaria. Oberyn moves closer and chastises them for being "pink little men who are far too slow on the draw." One of the soldiers reaches for his sword, and Oberyn quickly stabs him through the wrist with a dagger and tells the other that his friend will only live if he immediately gets help. Amidst the confrontation, Tyrion and Bronn enter, defusing the situation. After introducing Ellaria to Tyrion, Oberyn steps outside to speak privately with the Lannister dwarf. Tyrion asks Oberyn why he came to the capital, as Oberyn lazily dodges the question by confirming his invitation to the royal wedding. However, Tyrion knows he's lying and asks for the honest truth. Oberyn then informs that he remembers how Prince Rhaegar Targaryen wed his sister Elia Martell, and how his involvement with another woman, Lyanna Stark, was the catalyst that started Robert's Rebellion. He adds that the war ended with Tyrion’s father, Tywin Lannister, sacking the city while Ser Gregor Clegane brutally murdered Elia's children, then raped and murdered her. Oberyn orders Tyrion to tell his father that he's arrived and then warns him that “the Lannisters are not the only ones who pay their debts.”

Days later, King Joffrey and Queen Margaery's wedding ceremony takes place in the Great Sept of Baelor conducted by the High Septon and they are wed in front of gods and men. After the ceremony, the royals gather outside the Red Keep for a lavish wedding feast in celebration of the union of House Lannister and House Tyrell. Walking towards the feast, Lord Tywin Lannister and Lady Olenna Tyrell discuss the extravagance of their union between their grandchildren. Meanwhile, Prince Oberyn and Ellaria greet Tyrion upon their arrival to the feast. Along the royal banquet table, Lady Olenna then speaks to Sansa Stark and offers condolences over the recent Red Wedding massacre that resulted in the deaths of both her mother and brother, Lady Catelyn and Robb Stark. Olenna invites Sansa to visit her home of Highgarden some time when things settle down. During the exchange, Olenna toys with the girl’s hair and necklace in a grandmotherly fashion. After King Joffrey and Queen Margaery watch a group of minstrels play the Lannister song “The Rains of Castamere,” Margaery then rises to announce the leftovers of the large feast are to be given to the poorest in the city, which is applauded by the court. The king’s mother, Cersei Lannister, playing her part through gritted teeth, informs Margaery that she is an example to them all, though her dislike for the new queen is well-known.

During the feast, Prince Oberyn eyes the queen’s brother, Ser Loras Tyrell, with an obvious flirtation, to which Ser Loras intriguingly reciprocates. Loras then accidentally bumps into Ser Jaime Lannister as he stands in his spot as Kingsguard. After an apology, both knights talk about Lord Tywin’s arrangement of Jaime’s sister Cersei to wed Loras. However, Jaime informs Loras that he will never marry Cersei and that she would kill him and any child conceived on their wedding night. Loras replies that neither will Jaime, a subtle barb to their not-so-secret incestuous relationship. Afterwards, Prince Oberyn introduces Ellaria to Lord Tywin and his daughter Cersei, who subtly mocks Ellaria’s status as a bastard, instigating a debate over the cultural differences between the Dornish and the rest of Westeros. Ellaria seethingly states that there are bastards everywhere in Dorne. During this conversation, Oberyn makes a subtle comparison between the Lannister's ill treatment of his sister Elia's deceased children and the Martell's exemplary treatment of Cersei's daughter, Myrcella Baratheon, who has been safely living in Dorne for several years now, as she has been arranged to wed Oberyn’s nephew, Trystane Martell. King Joffrey then interrupts the tense moment and speaks to the court about contemplating history. Five dwarves then ride out of a large golden lion, dressed as and representing Joffrey, Renly Baratheon, Stannis Baratheon, Robb Stark, and Balon Greyjoy, each of the five kings in the War of the Five Kings. The dwarves put on a performance, jousting, fighting and making crude sexual acts which cruelly entertains Joffrey and Cersei, though is found too confronting by most of the court, including Oberyn, Ellaria and Queen Margaery, who watches her king with disdain. Sansa Stark makes little effort to hide her disgust during this satirical performance of the death of her brother Robb, as the dwarf portraying the late king parades around with a direwolf’s head. Ser Loras Tyrell leaves in anger after watching the crude depiction of his deceased lover Renly riding a mount that resembles himself. Once finished, Joffrey expresses his delight with the play and prepares to give the champion dwarf a purse, but then mockingly suggests that his uncle Tyrion should fight him as well. Tyrion cleverly counters this jape by suggesting that Joffrey should fight instead and show the same bravery he displayed at the Battle of the Blackwater, cautioning his nephew to be careful as the champion dwarf is "clearly mad with lust" and it would be a tragedy for the king to lose his virtue hours before his wedding night. Enraged and humiliated that his uncle outwitted him in front of his wedding guests, the king petulantly pours wine over his uncle's head and orders Tyrion to serve him wine as his cupbearer. Tyrion approaches Joffrey, who then purposely drops the goblet and kicks it under the table. Sansa hands the goblet to Tyrion, and he fills it with wine and hands it back to Joffrey. Oberyn and Ellaria witness the king demanding Tyrion to kneel before him but Tyrion refuses. Queen Margaery quickly interrupts the tense moment and informs that it is time to cut the pigeon pie. Joffrey then hands the goblet to Margaery, who then places it at the edge of the table near her grandmother Olenna. The king then draws his new sword, cuts the pie, and several white doves fly out. Sansa and Tyrion attempt to leave the feast but Joffrey commands Tyrion to serve him wine to wash down the pie. Tyrion hands the goblet to Joffrey and he quickly drinks all of it. Joffrey then tries to speak but begins coughing as he grabs his throat, while Margaery exclaims that he is choking. The king collapses face down and begins vomiting and convulsing, as Ser Jaime and his mother Cersei rush in and turn Joffrey over on his back. A former knight named Dontos Hollard then suddenly approaches behind Sansa and urges that she must escape with him now. Oberyn and Ellaria watch the Lannister siblings hopelessly hover over their dying son, as Joffrey then points an accusatory finger in Tyrion's direction, as Tyrion examines the wine goblet. Joffrey's eyes turn red while blood runs from his nose. The king then stops convulsing and dies in Cersei’s arms, who sobs with grief. In front of the royal court, she frantically orders her brother Tyrion’s arrest for the poisoning of her son.

Some time later, Lord Tywin interrupts Prince Oberyn, Ellaria, Olyvar and two prostitutes in order to discuss his son Tyrion's upcoming trial for the murder of King Joffrey. Once in private, Tywin brings up Oberyn's knowledge of poisons and the link between that and Joffrey's death, wondering whether Oberyn had assisted Tyrion. The topic quickly changes to the murder of Oberyn's sister Elia Martell by Tywin's "pet," Ser Gregor Clegane, during the Sack of King's Landing. Lord Tywin denies ordering her death, but promises to arrange a meeting between Oberyn and “the Mountain” so he can have his justice. He also offers Oberyn a position on the small council, if he agrees to act as the third judge during Tyrion's trial. Tywin explains that he is eager to bring Dorne back into the fold, wanting to unite the Seven Kingdoms against more obvious threats; citing that the Greyjoys are in open rebellion, a wildling army is advancing on the Wall, and Daenerys Targaryen is in the eastern continent of Essos with three dragons and building a powerful army. Tywin observes that only the Dornish successfully resisted Aegon Targaryen's dragons during his invasion of Westeros three centuries ago. Oberyn dryly notes it must be hard for Tywin to admit he needs the Dornish for help. Tywin admits that they need each other, who adds that he will help serve justice for Elia’s murder.

Some weeks later, in the throne room of the Red Keep, Oberyn attends the coronation of Joffrey’s younger brother, Tommen Baratheon, as the boy is crowned king of the Seven Kingdoms on the podium in front of the Iron Throne to enthusiastic applause. Afterwards, Oberyn is writing poetry in the gardens when Cersei requests a coversation. Oberyn admits that while he’s not a very good poet he learned from one his daughters, adding that he has eight kin. Upon discussing his family, Oberyn mentions his deceased sister Elia, to which one his daughters was named after. Cersei ponders that even as he’s a legendary and feared fighter of high station he still couldn’t save his sister, as she likens her own experience of losing her son. Oberyn then tries to ascertain whether Cersei truly believes her brother murdered Joffrey. When he mentions that the trial will reveal the truth, Cersei responds by saying “we will have a trial anyway,” insinuating that truth isn’t necessarily the result of a trial. Cersei then asks Oberyn of a favor as she hasn't seen her daughter Myrcella in over a year. Cersei asks him to have someone sail a new ship made for Myrcella down to Dorne since she missed her last nameday. Prince Oberyn promises to have the ship sailed down to the Dornish capital of Sunspear for Myrcella. Cersei then softly asks Oberyn to let her daughter know that “her mother misses her very much.”

Days later, Prince Oberyn attends his first meeting at the small council and complains about the early start-time. He pretends to be more concerned about the fancy title he will receive than matters of state, and refuses to rise when Lord Tywin enters the room. Tywin states that his son Tyrion's trial will begin that afternoon. An advisor named Lord Varys then informs the council of Daenerys Targaryen’s conquest of the slaver city of Meereen, as Tywin decides to take measures to prevent her from launching an invasion on Westeros. Oberyn warns the council not to discount the danger that the Unsullied army pose on the battlefield. Following the meeting, in the throne room, Varys ponders over Oberyn’s knowledge of Daenerys’ soldiers and asks if he has spent time in Essos. Oberyn confirms that he spent five years there, as he believes that because it is a “big and beautiful world” more people should take advantage of it. Oberyn grows tiresome of the conversation based on Varys’ lack of interest until Varys explains his general distrust for people. Oberyn then invites him to the brothel to share his story with someone. Oberyn then goes on to falsely assume that before his castration Varys was attracted to men. When Varys corrects him in saying that he was never attracted to women either, he asserts that his absence of desire allows him to pursue other things, as his gaze then shifts towards the Iron Throne.

Some hours later, Tyrion is brought to the throne room in chains, as his trial begins with King Tommen recusing himself. The three appointed judges sit on the throne’s podium to oversee the trial: Prince Oberyn, Lord Tywin and Lord Mace Tyrell of the Reach. With the trial quickly underway, Cersei has organized several witnesses to testify against Tyrion on the stand, such as Ser Meryn Trant and Grand Maester Pycelle, who exhibits the poisoned necklace given to missing Sansa Stark. Then to Tyrion’s surprise, Lord Varys testifies against him. Everyone provides strong, yet circumstantial, evidence of Tyrion's guilt. Tyrion seems particularly hurt by Varys' betrayal, so much that he asks the spymaster in front of the court whether he remembered what he had told Tyrion about his heroic efforts after the Battle of the Blackwater. Varys solemnly tells Tyrion that he never forgets anything. Following a recess, Tywin then orders a surprise witness to the stand: Tyrion’s former lover Shae. Her appearance astounds him, who had assumed she had left the capital. Shae testifies that Tyrion and Sansa planned Joffrey’s murder together, claiming that Sansa wanted vengeance for the murder of her family. She also confesses of Tyrion's sexual desires, much to Oberyn’s amusement but Tyrion’s embarrassment. When Tyrion pleads for her to stop she turns to look at him and bitterly says “I am a whore, remember?” Before she can continue however, Tyrion, enraged beyond sense, angrily demands that he be allowed to confess his crimes. He angrily roars about how he once saved King's Landing but should have let Stannis Baratheon kill everyone, much to the horror and disgust of the people in the court. Tyrion then claims to be guilty, as Tywin formally asks for him to admit to the court of the murder. However, Tyrion denies this, saying he is guilty of a "far more monstrous crime. I am guilty of being a dwarf!" Tywin scoffs at Tyrion's claims and says he is not on trial for being a dwarf. Tyrion angrily says he has been on trial for that his entire life. Tywin asks if he has nothing to say in his defense. Tyrion then says he has nothing to say in his defense, however, reveals his true feelings about Joffrey, denying the murder but saying he wished to have killed Joffrey himself. Tyrion then turns his fury towards Cersei and says that watching her "vicious bastard" die gave him more relief than "a thousand lying whores". He then roars to the court that he wishes to be the monster they think he is and would gladly give his life to watch everyone die from drinking poison. This enrages everyone in the court, as Tywin then orders Tyrion back to the dungeons. Before he can be escorted out, Tyrion bellows that he will not lose his life for a crime he did not commit and, knowing that he will get no justice from the court, demands a trial by combat. Oberyn’s face shifts with excitement as the rest of the court are in an uproar.

Days later, in his cell, Tyrion is approached by Prince Oberyn, who informs the dwarf of his disappointment in their first encounter as children. Oberyn and his sister Elia were told stories of the "Lannister Monster" and his extreme deformities. During a childhood visit to Casterly Rock, his cruel sister Cersei showed off Tyrion with great ceremony. Oberyn states to Tyrion, however, that he saw no monster, just a baby, adding that he and Elia were quite disturbed at Cersei's strong hatred toward Tyrion from such a young age. Tyrion’s eyes begin to tear, as he’s always been disturbed of Cersei’s hatred. Oberyn then tells Tyrion that he seeks justice for the death of his sister Elia, as Tyrion replies, "You are in the wrong place." Oberyn counters that he is in the perfect place; all those he means to bring to justice for his sister's murder are close at hand. Intending to start his revenge with Gregor Clegane, the knight who killed his sister, Oberyn offers his service as Tyrion's champion in the coming trial by combat.

Days later, Lannister guardsmen escort the shackled Tyrion to the arena, where a large crowd has assembled for the trial by combat. Tyrion grows apprehensive to find a helm-less Oberyn drinking, and wearing very light armor – in comparison to his opponent Gregor, who is clad in heavy armor. Oberyn dismisses Tyrion's concerns, noting that he always drinks before a fight and favors speed over protection. As Gregor makes his way to the arena, Ellaria becomes concerned, noting that he is the biggest man she's ever seen, but Oberyn  remains confident that he will emerge triumphant. She pulls Oberyn into a passionate kiss and warns him not to leave her alone in the world. After impressing the crowd with a display of acrobatic spear maneuvers, Oberyn goes on the attack, stabbing out at Gregor and constantly moving out of the knight's reach, forcing Gregor to tire himself out chasing his opponent. As he evades Gregor, Oberyn repeatedly taunts Gregor by consistently announcing his part in the murder of his sister and her children, demanding a confession, which only enrages Clegane further. As the “Red Viper” starts winning, Ellaria and Tyrion both witness with relief when Oberyn pins Ser Gregor to the ground with his spear. Their hopes, however, are quickly shattered in the moment when Gregor knocks Oberyn down and crushes his head in with his are hands, to the sound of Ellaria’s agonizing screams. With his fate sealed, Tyrion is struck with horror, as Lord Tywin states that the gods have made their will known and Tyrion is sentenced to death. Ellaria and Tyrion both stare in catatonic astonishment at Oberyn's skull-crushed corpse.

* In the aftermath of Oberyn’s death, follow Ellaria or Tyrion’s journey through the rest of the series.