"For thirty years," Klaus continues, "I have put the organic muesli and the expensive oat milk on the third shelf. That is what Primus demands. That is what REWE demands."

Klaus clicks the remote. A dusty projector hums to life, showing a slide of a perfectly stocked yogurt shelf. "Slide four," Klaus says, his voice flat. "The Principle of the Third Shelf."

She looks at him, puzzled. "The tall boy (der Große) usually puts it up high. But someone clever moved it down today."