The boisterous boy has dropped his paper napkin over the rail, and watches in horror as it flutters down among the book-browsing public.

“Dummy!” says his dad with a scowl.

The boy races down the aisle, round the corner and onto the escalator to retrieve his treasure from the ground floor. Drawing near, he looks up at the surrounding grown-ups with a face beseeching them to share his excitement, his dread, his amazement in this moment of catastrophe, but they walk right past the napkin on the carpet.

He snatches it up and runs.