Marcel had spent years mastering methods and memorizing theorems from Barbeau’s notes. He set two algebraic expressions side by side and, with Etta’s slip between them, watched as the air filled with slow, folding graphs. The tutor’s forms rose like paper cranes, unfolded, and matched—only slightly different in the way they held light. Marcel saw that the two were equivalent under a subtle shift: a translation and a scaling that preserved their essential shape, a small symmetry Barbeau had sketched in the margins of his book.