The story in three lines. Lan and Inkling fold Kami into a cup and step into a big room in New York in October 1958, where twenty-five people are at a folding lesson. Ruth wants to take a fold home to her little brother, who is in bed with a broken leg, but the teacher cannot come home with her. Lan pushes a finished cup into Ruth's pocket before Mark stops her. Ruth reads the chalk pictures on the board, folds the cup with the cast's help, and passes the test: she teaches a boy who has never folded one, without touching his paper, and Lan pours the water that proves it.

One question to ask. "Why couldn't Ruth just take a finished cup home?" The answer the story wants: a finished cup hides its folds, so it cannot teach anyone. Then ask why Ruth kept her hands off Joe's paper.

One thing to do at the table. Fold a paper cup together: diamond, bottom corner to top, both side corners across to the far edge, one flap down in front and one behind. Then let your child teach it to someone else in the house, using only words and their own paper. Sit on your hands while they do it. Whatever the learner gets stuck on is the step your child will explain better next time.

The grown-up layer. On 6 October 1958 Lillian Oppenheimer began a monthly folding lesson at the Japan Society in Manhattan; it grew into the Origami Center. She taught Scouts, hospital patients and people in nursing homes, wrote to folders around the world, and helped make "origami" the English word for it. Teaching something is one of the surest ways to find out whether you really know it. It is also how a fold travels from one room to a whole city.

Let your child tell the story back in their own words first.