Where do all the pens go?

The answer

In this made-up case from Matter of Record Files, every pen in Maisie's house had vanished. Inspector Fig searched the pen pot, the kitchen drawer, his own ear and Maisie's handbag, where he found three pens that were all borrowed. Then he heard a tiny clatter. The cat had been batting pens across the floor and under the fridge. Underneath were eleven pens, two lids and one very dusty biscuit. So the missing pens had a collector all along. The short ends with a real bonus clue about how a ballpoint pen works: it writes with a tiny metal ball in its tip. The ball rolls as you write, and spreads the ink across the page.