As Stannis Baratheon's ships sail to King's Landing, Matthos Seaworth assures his father, Davos, that come morning, the elder Seaworth will be Hand of the King. They have more men, and the Lord of Light on their side.
In King's Landing, Shae tries to comfort Tyrion Lannister, who is having trouble sleeping. Tyrion knows that the Lannisters won't survive the defeat, so Shae offers to "make love like it's your last day on earth," just like when they first met. Even more anxious, Queen Cersei secures a vial of nightshade from Grand Maester Pycelle.
In the evening, Bronn joins a group of Lannister soldiers at Littlefinger's brothel for some boisterous drinking. The crowd goes quiet with the arrival of the Hound, who refuses Bronn's offer of hospitality. The two exchange words and dirty looks, but the alarm sounds before the men come to blows.
Tyrion hears the bells from his chambers. His squire Podrick Payne dresses him while Varys shows him the city's secret underground tunnel system. Tyrion tells Varys that he will not run; he's the captain of the ship. Varys warns him that Stannis has taken up with a priestess and that dark magic has brought him to King's Landing. Shrugging off Tyrion's skepticism, Varys tells him that a man like Stannis cannot sit on the throne.
In the Great Hall, Tyrion gives instructions to Bronn: Wait until the ships are in the bay. Off to join the other high-born ladies in Maegor's holdfast, Sansa tells Tyrion she is praying for his safe return-like she's praying for Joffrey's. Joffrey shows off his new Valyrian steel sword, Hearteater, and makes Sansa kiss it for good luck. Unhappy when she insinuates he will not be in the midst of the fighting, Joffrey promises that one day the blade will be coated with Robb Stark's blood.
Sansa questions why Cersei-who clearly hates her-wants her in the holdfast. Cersei, already tipsy, encourages Sansa to drink and tells her that Ser Ilyn is there for the protection of the women. Spotting Sansa praying, Cersei mocks her and complains that she was born a woman, unable to do anything but babysit "frightened hens." She shocks Sansa with her regret that her womanly charms will have no effect on Stannis. "If the city falls, these women will be in for a bit of a rape," she says, including Sansa.
Tyrion quarrels with his nephew about strategy on the battlements. When Stannis' fleet comes into sight, Tyrion readies his archers, but does not give the order to fire. Only one royal ship sails into the harbor, leaking wildfire. Davos orders his sailors to steer clear, but it's too late: Tyrion has already signaled Bronn to fire a flaming arrow into the ship. The bay explodes with green flame; Matthos is among those thrown overboard. Certain that Tyrion has no more wildfire, Stannis orders his men to storm the beach, no matter the cost. The Hound goes to meet them directly, but he warns the archers to keep him away from their flaming arrows.
Still drinking, Cersei tells Sansa she hated being married off to a man she never knew. She strikes up a conversation with Shae and correctly identifies her as a low-born Lorathi. Cersei marvels that Shae has managed to become a royal handmaiden in just 10 years time and asks for the details, but Lancel, now injured, arrives to update the Queen on the battle. With the news that Stannis' soldiers are battering the Mud Gate, Cersei demands Lancel bring Joffrey back to his quarters. Turning to Sansa, she confesses that Ser Ilyn is really on hand to see that Stannis doesn't take them alive.
The Hound fights fiercely-and is saved from a hit by Bronn's arrow-but he is dazed by the fires burning around him. Unable to bear it, he abandons his post, despite Tyrion's pleas and Joffrey's orders to return to the battle. Lancel arrives to tell the king that the Queen has commanded him to the Red Keep. Tyrion intercedes and tells Joffrey he needs to lead his men, but Joffrey opts to follow his mother's instructions. Without Joffrey and the Hound, Tyrion picks up the mantle. In a stirring speech to the royal soldiers, Tyrion promises he has a way around Stannis' forces. "We'll come out behind them and f*ck them in their asses," he declares.
Lancel reports to Cersei that the battle is lost-their men lost hope when they saw the king leave the field. When he dares to ask Cersei to let him bring Joffrey back to the action, Cersei pokes his wound. Lancel's groans upset the women in the keep, but Sansa calms them with a hymn. Shae tells Sansa she needs to return to her room and keep her door locked-Stannis won't hurt her; Ser Ilyn will.
In her room, Sansa's is startled to find the Hound waiting for her. He tells her he is leaving and offers to return her to Winterfell, but she decides to take her chances in King's Landing. Tyrion successfully leads the Lannister forces through the tunnels, inspiring chants of "Half-Man." Just when he thinks he is safe, he shares a smile with Ser Mandon, who then tries to kill him. Pod drives a spear through Ser Mandon. Fresh soldiers, including one dressed in Renly Baratheon's armor, take the field. Stannis' men flee at the sight of "Renly's ghost."
Cersei sits with Tommen in the Throne Room and tells him a story about a brave lion cub as she readies nightshade for him to drink. Just as she puts the vial to his lips, the door swings open: Loras Tyrell, dressed in Renly's armor, enters, followed by Ser Tywin Lannister. The Lannisters have won.