A loud clang announced the angel's arrival the next morning. Both brothers, who had been unable to sleep soundly, were perched at the center table amidst tall, messy piles of books and papers. Castiel took in the mess, his ragged friends, and the knot of worry knit deeply into Dean's brow. "I got your call," he offered to Sam and Dean who stood up and approached him in unison.
"And?" Dean said, tone sharp with stress and exasperation. The wrinkles in his clothes suggested he hadn't changed in a couple days, and likely hadn't slept at all.
"And," Cass offered, "I came to take a look at it." He approached Sam, gaze already locked on the strange mark that almost seemed to glow on his neck. It wasn't something humans could see, but even grounded his angel eyes afforded him a little more insight. He wrinkled his nose as he got close. "You said she did this just before she died? What did she use to draw it?"
Sam's lips curled in disgust. "Her teeth."
"Hmm," Cass managed, reaching up to touch it. "And some of these occurred after the fact, you said?" Sam nodded. The angel's fingers grazed over the marked skin, and he noticed an unfamiliar warmth beneath the skin. Based on the thoughtful look in Sam's gaze, it seemed he had noticed it, at least partially. And based on the fact that Sam kept sneaking glances at his brother who was currently focused entirely on Castiel's examination, it also seemed like he had not informed his brother yet. Cass sighed. These two humans had a particular affinity for hiding their greatest ills from one another. "Does it hurt?"
"No, I can barely even feel it." Sam responded a little too quickly, and Cass swallowed a smile as Dean's attention immediately flipped to Sam. At least they could still read each other, even if they couldn't be honest. Still, Cass thought it better not to pry in front of Dean. He nodded, accepting that response for now.
"So?" Dean asked, tone even sharper than the first time he spoke. Cass fought the urge to roll his eyes. He knew Dean was only heckling him out of worry, but sometimes Dean treated him like an absolute idiot. He swallowed the hint of earthly annoyance and faced Dean calmly.
"So," he said, pausing first to give Dean a meaningful look, "I can't tell you what it's meant to do, but I have a guess as to how she did it, and what that might mean."
Sam saw the sarcasm welling in Dean's throat and spoke first to prevent another rude comment directed at the angel. "Honestly, we have next to no solid leads, so pretty much anything would help us at this point." Dean just huffed. Castiel focused his attention on Sam and nodded.
"I'm sure you have noticed at this point, but that mark is alive. I could smell it as soon as I got close." Sam's eyebrows dipped in confusion, but he didn't say anything. Cass continued. "When she placed that mark on you, she must have believed she wasn't going to survive the encounter. Magic like this is kept in reserve only for the most desperate of times. She left what I can best describe as a 'soul-mark;' she shaved off a layer of her soul and used it like thread, weaving it into your skin to form the spell. I've never seen it used with a sigil before, but the concept is the same no matter the spell work. It fuels the spell, keeps it active even after the caster's death. She attached her intentions to it, and the mark responds to them." Sam now wore a look that seemed to be a perfect blend of panic, confusion, embarrassment, and disgust. Dean's brow was now so low it was mashing his eyes back into his skull. Cass found his sudden resemblance to the Neanderthals amusing, but thought now was not the time to laugh.
"Do you know anything else about this….spell mark?" Dean said, sharpness finally curbed by the new information.
Cass sighed. "It's not active yet, which means it has a trigger, and with any spell there has to be a way to break it. There's no such thing as the perfect spell. Only a clever one, with a well-hidden key. The best way to find the key is to figure out what the spell is meant to do. And hopefully before it does it."
Sam let out a slow sigh. "So it's back to the books then."
"Or we could just stroll down the block to our friendly neighborhood witch and ask her," dean offered sarcastically, dropping back into his chair and shoving his notes out of the way, gaze back on the textbook in front of him. Sam huffed in agreement. "But there is no one around for miles," Cass said, confused. "And Rowena is hardly friendly; she's tried to kill you on several occasions." Sam stared blankly at the oblivious angel, and Dean just shook his head.