Leonard’s teenage niece is visiting Pasadena for a few days — part college scouting trip, part California vacation. She’s whip-smart, a natural genius, and has a playful, laid-back attitude that reminds Leonard a little too much of how Sheldon would be if he actually had social skills. While Leonard is busy in the kitchen grabbing snacks, his niece wanders into the living room and notices one of Sheldon’s whiteboards covered in a tangled mess of equations.

Out of pure curiosity (and a little bit of boredom), she picks up a marker and starts working through it. What was a knotted mess of numbers and symbols to anyone else just clicks for her — her brain moving faster than even she realizes. Within a few minutes, she neatly finishes the problem, underlines the solution, and casually tosses the marker onto the coffee table like it was no big deal. Then she goes right back to scrolling her phone and chatting with Leonard, totally forgetting about it.

A little while later, Sheldon returns home. He barely sets down his bag before his eyes zero in on the whiteboard — someone touched it. Outraged, he rushes over… but when he actually reads the board, he freezes.

The math — the math he’d been grappling with for an entire week, barely making any progress — was solved. And not just solved, but solved elegantly, cleanly, like it was simple.

His mind races. Who could have done this? A Caltech colleague? A prank? A random quantum fluctuation? He demands to know who touched his board. Leonard, confused, says no one’s been there except him and his niece.

When Sheldon learns it was her — a teenager, not even in college yet — he practically short-circuits. His entire worldview shifts slightly off its axis as he stares at her like she’s some rare, undiscovered scientific phenomenon.

Meanwhile, Leonard’s niece just grins and shrugs, completely unfazed “It wasn’t that hard, Uncle Leonard. You guys make this stuff way too complicated.”