Just outside the kingdom of Winterfell, Ser Waymar Royce, Will and Gared, three members of the Night's Watch, investigate some mysterious deaths. Will previously found a camp full of dead bodies, but the bodies have now vanished. Royce is attacked and killed by supernatural beings called the Others, but he rises from the dead to kill Will. Gared flees.
Bran Stark is a young boy who watches his father, Lord Eddard Stark, execute Gared for abandoning his post as a member of the Night's Watch. After the execution, Eddard's two older sons, Robb and Jon, discover a gigantic dead direwolf and her six living cubs. The children adopt the pups as their own. Back at the Stark castle, Eddard's wife, Catelyn, tells him that his friend Jon Arryn has been killed. The King, Robert Baratheon, is riding to Winterfell with all his knights and retainers to speak with Eddard about the problem.
In the far-off city of Pentos, Viserys Targaryen is making arrangements to regain power. Viserys is the son of the Targaryen king, who was deposed by Robert Baratheon 15 years earlier. He plans to marry off his 13-year-old sister, Daenerys, to Khal Drogo, a powerful warlord.
In Winterfell, Eddard welcomes Robert Baratheon. Robert and Eddard visit the grave of Eddard's sister Lyanna, the woman Robert loved and wanted to marry. Robert makes it clear that he is unhappy with his wife, Queen Cersei Lannister. Robert offers Eddard the chance to take Jon Arryn's place as the Hand of the King, his chief adviser and war commander. Robert also says that he wishes to betroth his son, the crown prince Joffrey, to Eddard's young daughter Sansa. That night, Catelyn Stark receives a message that says Cersei Lannister ordered the murder of Jon Arryn, the previous Hand of the King.
Seven-year-old Bran is exploring an abandoned part of the Starks' castle when he hears a man and woman talking. Bran peers through a window and sees Cersei Lannister and her twin brother, Jaime, having sex. When they discover Bran watching, Jaime throws him out of a high window. Bran's back and legs are broken by the fall, and his parents fear that if he ever wakes up from his coma, he will be crippled for life.
Daenerys Targaryen marries Khal Drogo in the city of Pentos. She cannot speak his language, but they still come to an understanding and consummate their marriage.
Jon Snow, Eddard Stark's illegitimate son, and Tyrion Lannister, the dwarf brother of Jaime and Cersei, ride with a group of men to the northern Wall of Winterfell. Jon is going to join the Night's Watch, a ragtag group of men who are exiled to the Wall to defend Winterfell against unknown threats. Eddard and his two daughters, Sansa and Arya, leave with King Robert for King's Landing.
Lady Catelyn remains at home to nurse Bran. She is still tending Bran when an assassin comes to murder the boy. She fights the assassin, and Bran's direwolf kills the man. Catelyn decides that she must travel to King's Landing to meet Eddard and warn him about the plots against his family. When she arrives in King's Landing, her childhood friend called Littlefinger tells her that the knife the assassin used to attack Bran actually belongs to Tyrion Lannister. Meanwhile, Eddard discovers that King Robert has bankrupted the kingdom with his constant requests for tournaments and lavish feasts. Littlefinger secretly leads Eddard to Catelyn, who tells him about the attempt on Bran's life.
Daenerys Targaryen gradually adjusts to life as Khal Drogo's wife. Her cruel brother, Viserys, accompanies Daenerys and Drogo on the long ride back to Drogo's country. Daenerys is finally tired of Viserys' mistreatment of her, and when Viserys attacks her, she makes him walk behind the company of horsemen in disgrace. Toward the end of the long journey, Daenerys learns that she is pregnant.
Bran has awoken and is having a difficult recovery in Winterfell. He is paralyzed from the waist down.
At Castle Black, Jon Snow meets Samwell Tarly, an overweight teenager who cannot fight. Jon befriends Samwell and protects him from the other boys.
On the road back to Winterfell, Catelyn Stark meets Tyrion Lannister and has him arrested on the suspicion that he ordered the attempt on Bran's life.
A courtier named Lord Varys tells Eddard Stark that Jon Arryn was poisoned after he started asking too many questions about the Lannisters. Eddard is horrified to learn that King Robert has almost no true supporters in the capital city. Almost everyone who surrounds the king is secretly loyal to the Lannisters.
Wild men in the mountains attack Catelyn and the group of men who helped her capture Tyrion Lannister. Tyrion saves Catelyn's life in the fight, and her attitude toward him softens somewhat.
King Robert wants Eddard to agree to help murder Daenerys Targaryen so that her unborn child will not one day threaten his kingdom. Eddard refuses and resigns as the Hand of the King. Robert tells him to return to Winterfell or risk execution. A short while later, Eddard and his men are attacked by Jaime Lannister, who wounds Eddard and kills his attendants. After Eddard heals slightly, King Robert apologizes to him and reinstates him as the Hand of the King. Eddard stumbles across some uncomfortable information about King Robert's children, and Eddard concludes that Queen Cersei's children are illegitimate. Cersei openly admits to Eddard that her twin brother, Jaime, sired her three children. Eddard advises Cersei to take her children and leave the kingdom because he intends to tell the king about her betrayal.
Catelyn arrives at Eyrie, the home of her sister, Lysa, the widow of Jon Arryn, the first Hand of the King. She finds Lysa in a mentally unstable state. Lysa imprisons Tyrion Lannister because she believes he has played a role in her husband's death. After Tyrion's champion wins a trial by combat, Tyrion is set free on the dangerous open road.
Daenerys arrives in the city of Vaes Dothrak to be presented to the medicine women, the dosh khaleen. Daenerys has to eat the fresh heart of a slaughtered stallion to prove that her child will be a strong ruler. At the feast after the ceremony, her drunken brother, Viserys, holds a sword to her pregnant belly and demands that Khal Drogo give him an army. Instead, Drogo melts some gold pieces and kills Viserys by pouring the molten gold on his head.
At King's Landing, King Robert lies dying and names Eddard as the Lord Protector of the kingdom. When the king dies, Cersei proclaims her son, Joffrey, to be king and has Eddard imprisoned. Littlefinger betrays Eddard, and it is revealed that Eddard's daughter Sansa also betrayed him unknowingly by telling Cersei his plans.
Jon Snow and other members of the Night's Watch discover strange bodies in the woods. The corpses have clearly been dead for a long time, but they haven't decomposed. Jon fights against one of the undead Others who invades Castle Black.
Robb Stark and all his bannermen ride away to King's Landing to free Eddard from the Lannisters. Robb leaves Bran in charge of Winterfell.
An attempt is made on Daenerys Targaryen's life, and when Drogo learns that King Robert has sent assassins to kill Daenerys, he decides to take all of his warriors and invade the Seven Kingdoms.
Tyrion Lannister recruits several armies of tribesmen to support him in upcoming battles. Tyrion meets his father, Tywin, at a roadside inn and learns that the Lannister armies have been winning battles all over the land. Tyrion's tribesmen agree to fight with the Lannisters against the Starks. Tyrion and Tywin win a battle against some of the soldiers sent by the Starks, but meanwhile, Robb Stark and Lady Catelyn win another skirmish against the Lannisters and capture Jaime Lannister.
After sustaining a severe wound in battle, Khal Drogo lies dying. A healing woman named Mirri offers to do a dark magic ritual that will save Drogo. Drogo's men begin to fight each other, and the camp is in chaos. Daenerys is dragged into the tent where the ritual is happening, and the dark magic kills the child she is carrying. When Daenerys wakes, she learns that the dark magic has saved Drogo's life but left him in a permanent vegetative state. She smothers her husband to end his ruined life.
In King's Landing, Arya Stark is disguised as a beggar child, and she watches as her father, Eddard, is publically executed. Sansa is still betrothed to young King Joffrey, who abuses her and enjoys frightening her.
The Stark armies gain ground. Instead of supporting one of King Robert's brothers as successor to the crown, many lords decide that they will only follow Robb Stark, who they wish to crown as King in the North.
Daenerys builds a funeral pyre for her husband. As his corpse burns, the three dragon eggs that she places on the pyre begin to hatch. Daenerys and her dragons instantly draw the adoration and loyalty of many people, who will one day form her army.