Contains spoilers for this episode and earlier episodes.
Davos leads Stannis's ships into Blackwater Bay, where an unmanned vessel waits for them. At Tyrion's signal, Bronn fires a burning arrow that ignites the wildfire, destroying ships and throwing the attackers into chaos. Stannis orders the survivors ashore and advances on the city gates. Inside the Red Keep, Cersei shelters with Sansa and the other women, with Ilyn Payne ready to kill them if the city falls. Cersei drinks and describes what defeat would mean for the women inside.
The Hound's fear of fire overwhelms him, and he abandons the battle and Joffrey. Cersei sends for her son, whose retreat damages the defenders' courage. Tyrion rallies the men himself and uses a tunnel to attack Stannis's soldiers from behind. Sansa tries to calm the women before Shae urges her to leave. In her room, the Hound offers to take her north, but she stays. Outside, Tyrion's counterattack is met by more enemy troops.
Mandon Moore turns on Tyrion and cuts his face, but Podrick kills the knight before he can strike again. Reinforcements arrive, including Loras in Renly's armour, and smash into Stannis's forces. Stannis wants to keep fighting but is pulled away by his men. Cersei sits on the Iron Throne with Tommen, preparing to poison him rather than let him be captured. The doors open before she acts, and Tywin announces that they have won.