Hmmm.... Okay I did not get the bromance I was looking for in this episode in the way that I was expecting, but what actually happened might be better. Let's look at the plot first, though.
Sam and Dean are taking a break to recuperate after the whole Demon!Dean ordeal. However, Dean is restless. He notices something that looks like a string of werewolf killings, and he tells Sam that he needs the hunt. Sam makes Dean promise to tell him if he starts to lose it, and Dean agrees.
They investigate the killings, and, using different witness accounts, they trace a woman back to her hideout, only to see that it's Kate, from "Bitten," a Season Eight episode. They tie her up and Dean prepares to kill her, but Sam says that maybe he should be the one to do it, because Dean's not ready. At this point, Sam gets a call saying that there's been another kill, very recently. So... Kate can't be the guilty party. Kate escapes, but Dean had grabbed her cellphone earlier, so they can use that to track her down.
As they try to find Kate again, Dean questions why Sam would try to stop him from killing Kate. Dean wonders if Sam is ready to be back on the hunt, because of what he did to Lester. Dean speculates that there might have been other people that Sam condemned to Hell, but Sam says Lester was the only one.