After seeing the events that have occurred over the past 4 episodes of this awesome game I believe that what might happen in the end of episode 5 is this. It's only Clementine and Lee left after an epic final fight with the mystery kidnapper. Walkers suddenly surround the building and after looking for a way out they find that this time there is no escape. That's when Clementine shows Lee she is also bitten, then it comes to Lee's attention that the gun he has with him only has one bullet left. The player must make the ultimate final choice.