In the opening scene of Episode 5 of A Knight of the Seven Kingdoms, the impending duel is the centerpiece. Baelor Targaryen speaks of the sobering reality they face, a harsh reminder that this is not going to be an easy task. As Baelor decides to face the Kingsguard himself, given their inability to touch royalty, we see Dunk join the others in donning their helmets and preparing for battle.

Dunk's fate, however, is short-lived. He is immediately stabbed with a lance by Aerion and struck in the face with a Morningstar. He topples off his horse and lands in a heap on the ground.
We then jump back in time and see flashes of Dunk as a child. In the aftermath of battle, he scavenges for gear and loot with his friend Rafe in the heart of Fleabottom, a tinderbox of hurt just waiting to ignite.
When they head back to town, Rafe and Dunk are confronted by the vicious Alester. He's another opportunist and questions what's in their bag. When he's distracted by a ruckus, Rafe decides to rob an ale skin from him.
Dunk's outlook on life here is bleak, but he still clings to the faint possibility of his mother coming back. He and Rafe have been saving and looting for a while now to gain passage across to the Free Cities. Despite getting the right amount of coins, the end of the War against the Black Dragon (something that's referenced a lot in these flashbacks) and an increase in ferrying people out of Kings Landing have seen prices double. For now at least, they're not going anywhere.
It's here where Alester returns and demands the pair return his stolen ale skin. When Rafe boldly proclaims they've sold it, he takes their purse and slits Rafe's throat when she tries to steal from him again.
When Dunk jumps into fighting, it's Ser Arlan of Pennytree who comes drunkenly stumbling out of the back of the pub, fighting with Alester and his fellow goon. Arlan saves Dunk's life, and with Rafe dead and their future bleak, Dunk decides to follow Ser Arlan from a distance.
Just as he had done with Egg, Dunk seized the opportunity to present himself as Ser Arlan's squire. Initially, he kept a cautious distance, but sickness and weakness began to claim him. Ser Arlan saw this and brought him in as his squire.
In the present, Dunk and Aerion found themselves wrestling in the muddy arena. Dunk was stabbed repeatedly and even received a dagger through his hand. It was a brutal skirmish, as Dunk lost an eye and Aerion suffered a blade wound across his inner thigh.
Despite being almost overcome by the pain, Dunk mustered every ounce of energy he had left and got back to his feet. This courageous act saw the entire crowd rally to his cause, much to Aerion's shock. Dunk eventually emerged victorious as Aerion yielded. This ended the conquest and Dunk's team won!
Baelor promised to get Dunk the attention he needed... but there was a problem. He had Steely Pate and Raymun Fossoway help remove Baelor's smashed helm, which seemed to have a broken visor too. However, when the helmet came off, it was revealed that Baelor was missing a significant portion of his head due to a nasty blow from Aerion earlier in the conquest.
Baelor turned, collapsed on the ground, and fell straight into Dunk's arms. He began weeping and apologizing constantly, as this death was likely to have far-reaching ramifications going forward.