Brief summary that was too long to write earlier:

Basically what happened was that when Hector was fighting Patroclus (disguised as Achilles), his helmet got knocked off and Hector saw that it wasn't Achilles whom he was fighting. Hector and his men take Patroclus prisoner while Achilles believes they have killed him and have taken his body, hence Achilles' anger and hate for Hector. When Achilles challenges Hector, Hector doesn't have time to tell Achilles that his cousin is still alive. Achilles proceeds to kill Hector, prince of Troy, and takes his body back among the Myrmidons like, as he thought, Hector had taken Patroclus' body back to Troy.

"Damn!"

Patroclus had forgotten his manners and swore. He didn't care. He kicked the ground as he swore again. He ran a hand through his tousled blonde hair and sighed. He looked around the cell. It was dark and poorly lighted. Why shouldn't it be? Why did prisoners of Troy need to see anything but their death?

Patroclus wasn't sure whether to thank or curse the Trojans for sparing his life earlier that day. Why did Hector let him live? He was going to kill him eventually, was he not? Maybe Hector was thinking about the idea that Troy would fall. It surely would, no doubt in Patroclus' mind. But what if Hector was thinking to that day? Maybe he believed that by sparing Achilles' kin that maybe Achilles would spare Hector's family if it came to that.

Maybe the prince had common sense after all. Patroclus was almost surprised that, when he ran up that hill to face Hector as Achilles, that no one stopped him. Not even remotely noticed, actually. Well, maybe that was just because Achilles had taught him how to fight. How to fight like him.

Patroclus shrugged and leaned against the cold hard wall. The floor was sand and dirt, nothing more. He slid down the wall and onto the sand. He could see the footprints of other men still imprinted in the ground. Where were those men now? He shivered at the thought. Wherever they were, he would surely be joining them.