Carter propped a foot on the bar of Lincoln’s stool and leaned in. “Oh, baby, talk dirty to me.”
Lincoln covered his face with his hands and laughed. No other choice, and Carter laughed with him, warm and bright, and it was a welcome respite after hours of grinding work. Smiling, he peeked out from behind his fingers at Carter. “Thank you.”
He returned the grin. “You’re welcome. Now, show me what you got.”
“You were right that Jeremiah’s gray hair is a genetic variant versus mine, which is a result of old age.”
“Seasoned, L. The word is seasoned.”
“Yes, well, Jeremiah has not seen as many seasons as me. Though I’d bet he’s seen more hospitals.” He tapped at a genetic marker on the screen. “This is a frameshift mutation that is associated with increased susceptibility to Crohn’s disease, which in this case may also be a founder variant.”
“English, Professor.”
“You were doing so well with the science-speak before.”
Carter held a hand up at about the level of Lincoln’s chin. “Limits, remember.”
Lincoln chuckled, lowering Carter’s hand, his own lingering on his longer than strictly necessary before he withdrew it. “A founder variation, or the founder effect, occurs when a small population separates from a larger population, thereby cutting off the gene pool. So if there are any anomalies in that gene pool?—”
“They’re likely to get replicated.”
“Exactly. Take the higher incidence of Huntington’s disease among Dutch Afrikaners, fumarase deficiency in LDS members, or polydactylism in Amish populations. Segmented populations, by geography, religion, or choice, where gene pools are limited and anomalies replicated.”
“Which in the original Apex population may be premature gray hair and Crohn’s disease?”
“Premature gray hair is the thing we can visibly see. Jeremiah also having Crohn’s may just be a coincidence, but autoimmune conditions, such as Crohn’s, have been linked to premature graying.”
“What about the frameshift thing you mentioned?”
“Right, so DNA base pairs come in sets of three. A frameshift variation occurs when a base pair is deleted or inserted, and it is not in a set of three, so it causes a disruption in the chain. Increased susceptibility to Crohn’s can arise from, among other things, a frameshift variation.”
“And if that frameshift variant existed in an isolated population?”
“It could also be replicated, passed down, and characterized as a founder variant.”
“We need to call this in,” Carter said, already pulling out his phone.
Lincoln laid a hand over his, stilling it before Carter could call Beverley. “Like I said, the Crohn’s disease could just be a coincidence.”
“But not the premature graying. That seems statistically relevant, yes?”
Lincoln nodded.
“Good. All that work I just put in at the library won’t go to waste.”
“What’d you do?”
Carter swiped Beverley’s contact away and opened his photos, then held the phone so Lincoln could see. “Using the time windows established for Dr. Fear’s earliest cycles, I started going through photos, particularly town events, where so-called founding families would most likely be, and I flagged those with baby silver foxes.”
Lincoln flipped through the pictures, most of them in color, making the young silver-haired persons stand out even more. He paused on one, a shot at a ribbon cutting. He spread his fingers to zoom in on the uniformed officer. “Is that Barry?”
“Maybe, or it could be their father, or Larry. They all looked similar in the photos I saw at the station. I can’t be sure without asking them or doing more research to conclusively ID everyone in the photo.”
“Asking them will blow our cover, and if the police are involved . . .”
Carter nodded. “We can’t blow our cover.”
“You’re right, though.” Lincoln closed the photo app and handed the phone back to Carter. “We can call this much in. Let’s get forensics to double-check evidence from the past scenes. Hair samples especially. At least two of Dr. Fear’s victims were older and had gray hair. Let’s confirm any gray hairs collected at the scene were theirs. If there were gray hairs found at the scene that aren’t theirs, then maybe those belong to Dr. Fear. And if none from past scenes are found, let’s see if any were or can be found from the scene where Ruby and Chase were taken. Neither of them has gray hair.”
