"Or," Sam glanced at Cas. "I don't see why Cas can't go with us, too." Cas could be quiet, he could fade into the background if he really wanted to. Sam couldn't be sure he wouldn't show up at the office, whether or not Sam asked him to go, but Sam saw no reason to try and exclude him.
Lydia's story was an interesting one. Totally different from Sam's life history, and yet shockingly similar. At least the over tones were similar. Most people didn't know about werewolves and other odd occurrences, but Lydia was clearly right in the middle of it where she came from, kind of like Sam was right in the middle of things.
He couldn't think clearly enough through the facts and details to offer a theory, but something was taking shape in his mind. All he really knew, though, and what he chose to focus on was the fact that Lydia was his friend, and that was the most important thing.