The Case (Whittle · Tablo · Reeve)

Reeve went first, because Reeve always started where the sources were. She spread the three witness notes and the logbook side by side and read across them. "Two witnesses never spoke to each other," she said, "and they both say the person moved quietly and knew exactly where things went. That agreement is real — our librarian works here or knows the library cold." She found a disagreement too: one note said "tall," the logbook implied "short enough to use the low shelves without a stool." She tapped the fork. "There. One of these is wrong, or 'tall' meant something else. Either way, height is where the sources argue — so height is a live question, not a settled fact." She'd turned a pile of accounts into two solid facts and one sharp question, and handed it to Tablo.

Tablo took Reeve's facts and built her grid. Nine suspects down the side; every trait across the top — works in the library, knows the shelves, height, on-site after dark. "Reeve says our person knows the library cold," she said, and drew a hard line through the four suspects who'd never set foot in it. "Gone." She crossed cells clue by clue, each elimination cascading into the next. "This one was away all week — gone. This one can't reach the low shelves or the high ones — gone." The nine became five, became three, the grid filling with crossed-off cells until — she stopped. Three suspects remained, and every remaining clue fit all three equally. "I'm stuck," she admitted. "I've eliminated everyone I can. These three are identical on every clue I have. The grid can't split them." She'd narrowed nine to three by pure elimination — and hit a wall the grid couldn't climb.

That was where it nearly stalled — and where Whittle grinned, because a wall of three indistinguishable suspects was his favorite thing in the world. "You can't tell them apart with the clues you have," he said. "So we get a new clue — and we design it to split them." He held up the height question Reeve had flagged. "Two of your three are about the same height. One is noticeably shorter. If I can find one fact about height, it doesn't just tell me about height — it cuts the three in half." He proposed a single sharp test: check which of the three could have reached the top shelf where a book had been reshelved without the stool, which was still locked away that night. "I don't need to know everything," he said. "I need one question whose answer eliminates the most suspects. One good cut beats ten random facts." They ran his single check. It cleared two suspects instantly. One name remained.