Sam carried the key that he'd found with him whenever he went out. Just in case. He'd done some research on the symbol carved into the key and had found mostly rumors and speculation and nothing concrete. He still didn't know why the City had left it for him or what he was supposed to do with it, but he was intrigued.
Unfortunately, his research was just leading to further questions. Which was why Sam took to long walks around the City. If it wanted him to do something with the damn key, it'd show him the place, right? Maybe.
He was just about ready to turn around and go home when he spotted the doorway. It looked like an underground bunker
or something. He couldn't help but wander a little closer since he hadn't seen this particular doorway before. Upon closer inspection, he saw a symbol carved on the handle that matched the symbol on the key.
Sam's breath caught with excitement and he tried not to get his hopes up too much as he fished the key out of his pocket and tried it.
His jaw dropped ever so slightly as the key worked and the door pushed open. He moved forward onto a balcony overlooking what could only be described as a war room. It had a switchboard, a ham radio, and a telegraph. As he moved further in, he spotted a room lined with books off of the circular war room. He was naturally drawn to the books and started to investigate. It was only once he looked a little bit that he realized that this was the sort of library he could get lost in.
"What is this place?" Sam murmured as he traced the titles of tomes thought long lost and those that he'd never even heard of on everything from demons to werewolves to just about every other piece of mythology he could imagine.
He finally started looking at the card catalog, which was extensive. And next to that was a membership roster. Sam opened it up and saw the same symbol with the title "Men of Letters." He silently scanned the membership roster, though he wasn't sure why. It was only when he came to a familiar name that he stopped, blinked, and then stared at the page until the letters no longer seemed to make sense.
His dad hadn't talked much about their grandfather except to mention that he'd left when dad was young. But he had mentioned the name. Henry. Was this a coincidence? Or a trick of the City?
All Sam knew was that he wanted to share this with his brother. This place seemed filled with questions and together they could maybe find some of the answers. Sam took out his cell phone, fully expecting to have to step outside to make this call. After all, an underground bunker wasn't the best place to make a call. He was surprised when he saw that his phone had full signal in here. Not wanting to question it for now, Sam dialed the phone and waited for Dean to pick up.