Season 1 spans a period of several months on a world where the seasons last for years at a time. The action begins in the unified Seven Kingdoms of Westeros as the long summer ends and winter draws near. Lord Eddard Stark is asked by his old friend, King Robert Baratheon, to serve as the King's Hand following the death of the previous incumbent, Eddard's mentor Jon Arryn. Eddard is reluctant, but receives intelligence suggesting that Jon was murdered. Eddard accepts Robert's offer, planning to use his position and authority to investigate the alleged murder. Meanwhile, on the eastern continent of Essos, the exiled children of House Targaryen, which Robert destroyed to claim the throne, are plotting to return to Westeros and unseat the 'usurper'. To this end, Viserys Targaryen arranges the marriage of his sister Daenerys to Khal Drogo, the leader of 40,000 Dothraki warriors, in return for the use of his warriors in invading Westeros. For her part, Daenerys just wants to find a safe refuge far away from King Robert's assassins and her brother's scheming ambition. Finally, on the northern-most border of the Seven Kingdoms the sworn brothers of the Night's Watch guard the Wall, a 300-mile-long colossal fortification of ice which has stood for thousands of years. The Watch defends the Wall against the depredations of the lawless wildlings who live beyond, but rumour speaks of a new threat arising in the lands of perpetual winter.
Season 2 spans several months on a world where the seasons last for years at a time. The Seven Kingdoms are at war, with the King in the North, Robb Stark, fighting to win independence for his people and those of the Riverlands. Robb decides that he must win the allegiance of the fiercely independent ironborn to his cause, and sends his best friend Theon Greyjoy to treat with his father, who is hatching plans of his own. Meanwhile, Joffrey Baratheon holds the Iron Throne with the backing of the powerful House Lannister, but his uncle Renly has also claimed the throne with the support of House Tyrell, whose armies are much larger. As they struggle for the throne, Tyrion Lannister arrives in King's Landing to take matters in hand, only to face opposition from his scheming sister, Cersei, now the Queen Regent. However, there is another faction entering the picture. Stannis Baratheon, Robert's younger brother and Renly's older, has also claimed the Iron Throne. A proven battle commander and veteran of several wars, Stannis is known to be utterly without mercy to his enemies and will do what is right even if it destroys him. Advising him is Melisandre, an enigmatic priestess from the east, who believes Stannis is meant for a greater destiny, and Ser Davos Seaworth, an honest and honorable man uneasy with the shifts in power at Stannis' court. Far to the east, Daenerys Targaryen has hatched the only three dragons in the world. Eventually they will grow into terrifying monsters capable of destroying cities at her command, but for now they are still hatchlings and vulnerable. With her khalasar gone, Daenerys and her small band of followers must find a way across a forbidding wasteland and find new allies to support her claim to the Iron Throne. In the distant north, the Night's Watch has mounted an expedition beyond the Wall, searching for missing rangers and investigating rumours of wildlings gathering in the mountains. For Jon Snow this will be a rite of passage as he is asked to make difficult choices, for the realm and for himself.
Season 3 spans several months on a world where the seasons can last for years at a time. Autumn has fallen across the world, with winter not far behind. The people should be preparing for years of snow and ice, but the Seven Kingdoms of Westeros instead remain gripped by civil war. Would-be king Renly Baratheon has been assassinated, altering the alliances in the war. The cruel boy-king Joffrey Baratheon has won a great victory by securing an alliance with House Tyrell, with his supporters defeating his uncle Stannis in an epic battle. Joffrey now commands the largest armies in the realm and his triumph appears inevitable. King Robb Stark remains in the field, however his homeland, the North, is partially under ironborn occupation. Robb needs to decide on a course of action to win an overall victory. He must also win back the allegiance of House Frey, whom he has offended by breaking his marriage pact to them. King Robb has won every battle he has fought, but as with old King Robert, the Starks will have to see if good soldiers make good kings. Stannis Baratheon may be defeated and most of his army destroyed or scattered, but he is not out of the fight yet. Having retreated to his headquarters on Dragonstone island with his handful of surviving soldiers, Stannis' status as the last legitimate heir to his older brother Robert still casts a shadow over Joffrey's claim to the throne. With the priestess Melisandre at his side, Stannis can still influence the course of the war by striking where least expected. The lives of many others still hang in the balance. Bran Stark and his protectors must cross the frozen wastelands of the North to reach the Wall, whilst Arya must brave the war-torn Riverlands in search of her mother and brother. Brienne also has the thankless task of taking the captive Jaime Lannister home across hundreds of miles of battlefields and carnage. Theon Greyjoy must face the consequences of his actions at Winterfell. And in King's Landing both Tyrion Lannister and Sansa Stark must brave the currents of a much more dangerous court in order to survive. On the eastern continent, Daenerys Targaryen has fled the political viper-pit of Qarth. Her dragons are growing and her fame is spreading, but to take the Iron Throne she will need supporters and an army. Both may be found in the corrupt cities of Slaver's Bay... for a price. Beyond the Wall, the White Walkers are on the move, threatening both the Seven Kingdoms and the lands of the Free Folk. While the Night's Watch faces the threat of the White Walkers in the field, Jon Snow must infiltrate the wildling army of Mance Rayder and discover the King-Beyond-the-Wall's plans.