WARNING: Characters with Spoilers attached ahead!! I only mentioned the basics, but beware looking them up on the supernatural wiki! You will get a ton of spoilers and you won't be able to go back! If you are up to date on the show and just don't remember the name, though, you should be safe.

The brothers went to their separate corners to cool down after their fight. They knew that trying to talk it out at this point would only end in another shouting match, and neither really felt like yelling at each other. They had each said their piece, paired with a few hurtful words laced with their concern for one another, and now it was time to refocus. Sam made sure to make a trip to the library from time to time to grab something else to read. He didn't want Dean thinking he was slacking, but couldn't stand to sit in the same room and deal with the passive glares Dean often threw at him after a fight.

Dean had forgiven Sam mere moments after their fight, but he felt it was important to let his words simmer a bit. He knew that Sam had been a little right; he had gotten himself a bit worked up about all the unknowns surrounding the thing on his brother's neck. It wasn't that his concern was misplaced, because he knew there wasn't one time when he and his brother actually caught a break. It had always been a series of shit-shows, failed rescues, and repeated deaths. Their only break so far was that nothing had successfully kept them dead yet. He didn't want to have to cross that line again this time.

Still, Sam seemed to be feeling better than before, and the mark hadn't developed further since that first night back at the bunker. Dean wondered why that was. It had grown significantly in the first eight hours, and Sam had clearly felt it. Why was it dormant now? While he hadn't said anything directly, Sam was acting like he already knew what had caused it to spread, and was simply working to prevent it on his own. The fact that he wouldn't share his theory with his brother worried Dean. What was so secret that he couldn't even rely on his own brother?

After a few hours of solid work, Dean made his way to the kitchens. Sam had been staying in his room, probably assuming Dean was still mad and needed some space. But Dean's anger had simmered out hours ago, mostly thanks to the sleep he had just gotten. Which meant that even though he would never say it out loud, Sam had been right. And Dean realized that he had probably worried Sam almost as much as he was worrying himself about the mark. While it was underhanded and dirty, Sam was only trying to help. That meant that even though he wasn't going to let up on the research, he would make an effort to exercise at least a little more control.

Dean grabbed a couple of beers from the fridge and made his way to Sam's room. The door was open, and Dean found Sam crammed into the tiny desk, one leg splayed to the side because they both simply wouldn't fit under the table. He was propped up on one elbow, stretched awkwardly to the side; Dean could tell by the way Sam's head rested on his hand that he was about five minutes from either changing position, or giving up entirely. Four books lay open on the bed, and the heavy tome Sam had been favoring perched atop the desk amidst papers and file folders. Dean let out an amused sigh. He had no right to say Sam hadn't been taking this seriously. His meticulous nature wouldn't let him slack off on the research, even if he didn't want to do it.

"Find anything?" Sam asked, turning to face him. Dean had been watching him from the doorway for a couple of minutes without speaking, and the feeling of his eyes on his back made reading surprisingly difficult.

"Yeah," Dean replied, curbing his usual sarcasm to keep Sam from getting defensive, "no. Not really." He tossed the beer to Sam, who caught it deftly and twisted off the cap, letting it clatter on the desktop. Sam let out a quiet breath and opened his mouth to apologize. Dean spoke over him. "I get why you did it, Sam. Just—don't drug me next time, okay?"

Sam looked relieved. "Sure. As long as you sleep from time to time." Dean let out an exasperated breath and took a swig from the bottle in his hand. Sam did the same. They remained like that for a few minutes, comfortable in each other's company. Then Sam cleared his throat.

"So I actually did find something, a couple of hours ago." Sam said, averting his gaze and instead focusing on the sheet of paper that lay in front of him. He knew Dean was now making that closed-eyed annoyed face of his, but continued on before Dean could retort. "I found that passage in this book earlier, which didn't have any additional info on that section, and I couldn't find a signature on the notes to figure out which Man of Letters had written it. Usually they sign off on each piece of research, like meeting minutes.

"But I got the feeling that I had seen this writing style before, you know, the way he uses modifiers on his opening sentences and usually concludes with a really long ending paragraph."

"You are such a nerd," Dean interjected, unable to resist.

Sam rolled his eyes. "Do you want to know what I found or not?" Dean just smirked at him. Sam sighed. "I decided to flip through the member archives to see if I could match the writing style to one of the members on file. And I found a match. Remember our dear friend Cuthbert Sinclair?" Dean's lip curled in recognition of the name. Sam was careful not to linger on the name too long. "As you might remember, he was directly initiated as Master of Spells when he joined the men of letters. He knew all sorts of spells, including but not limited to—"

"Sigils." Dean said, focus evident in his voice. He let Sam continue.

"Right. Now, unfortunately, he was such a genius, he rarely took notes."

Dean sighed. "Great." He took another swig of his beer.

"But," Sam added in the dramatic voice he always used to get to his final point, "his student did."

"His student?" Dean asked, looking confused.

"Yeah," Sam said, a satisfied smile perched on his lips. "Henry Winchester."