Darnell: “Yeah.”
Vaughn just wanted to leave the woman alone, but Darnell was blocking him in.
“Numbers on their chests, numbers on the boxes, different numbers in the boxes?” Ivy said. Her voice was different somehow. Far-off.
“Well, it’s the same ten numbers repeated.Uh, two, three, seven... thirteen.”
“Two, three, five, seven, eleven, thirteen, seventeen, nineteen, twenty-three, and twenty-nine.”
“How’d you know?” Darnell asked.
“Those are the first ten prime numbers.”
“Ah.”
“The boxes... ?” Darnell pressed. “Any idea what this all means?”
Ivy didn’t answer at first. Her brow still stitched, she ran a hand through her hair. It got stuck halfway and she teased her fingers free.
“Ten numbers, ten boxes, ten...” Ivy trailed off before saying the word “victims.”
“Yes,” Darnell confirmed. He kept shooting these looks at Vaughn, which he found particularly annoying.
“Have either of you ever heard of the 100 prisoners problem?”
Now it was Vaughn’s turn to stare at Darnell. The big man shrugged.
“Can’t say that I have,” Vaughn admitted.
Ivy’s forehead softened, and the ‘11’ fold between her eyes disappeared completely. When she spoke again, she seemed more or less steady.
It was as if her brain switching into math mode had made her forget all about Aaron Treadman.
“It’s a classic probability theory in the form of a game. One hundred prisoners are placed in a room and are given the rules: each one is assigned a unique number from one to one hundred, consecutive. They are all to enter an adjacent room alone, one at a time. They can discuss strategy beforehand, but once they are in the room, they can no longer communicate with the other players. The room has one hundred boxes in it, all labeled consecutively, again, from one to one hundred. They can open up to fifty boxes, and that’s it. The numbers inside the boxes have been randomized. Their goal is to find their number—the one assigned to them—in one of those fifty boxes they open. If they do, they have effectively ‘won.’ The boxes are closed again, and the next person enters the room. Same rules apply. If all one hundred find their number, they’re released from prison. If even one of them fails, they all lose.”
“They die?” Vaughn blurted.
“Yes. These are prisoners, remember? Anyway, it’s just a hypothetical game. Win the game, you live. Lose, you die.”
“I mean, depending on the sentence, it seems like a good deal. Fifty-fifty, right?” Darnell said, playing along.
“Not exactly,” Ivy continued. Vaughn recognized her now as the same woman in the video. Confident and sure of herself, despite the uncomfortable analogy she’d used on TikTok. “For the first person to enter the room, the odds are, like you said, fifty-fifty. But for every one of the one hundred prisoners to find their number? Opening only half the boxes? The formula is one in two to the exponent one hundred.”
One of Vaughn’s eyebrows lifted. He felt impossibly stupid at this moment.
“It’s... not fifty-fifty?”
Darnellsoundedimpossibly stupid at this moment.
“No. It’s more like less than one in a decillion.”
What the fuck is a decillion?
Vaughn had just recalleddecuple, as in decuple homicide. He wasn’t in the mood to learn another number, and decillion sounded somehow even more ominous than decuple.
“Awhat?” Darnell asked.
If Darnell Sacker had a superpower, it was this: the ability to not give a shit how he looked in front of others. He just wanted to understand, to find the bad guy. He would ask question after question until he exhausted a suspect.
