Later in the day, following the affair of the foil wrappers, I discovered by accident another clue that might help to explain the noise in the night. I can't say how long the clue had been there because, being male, I rarely look much beyond whatever requires my immediate focus, and this is every bit as true in the kitchen as anywhere else. But something made me lift my eyes that day and there, clinging to the topmost edge of the topmost tiles on the kitchen wall, was a line of little turds. And I don't mean people.

I gaped.

Each little turd was ringed in chalky white, a textbook example of budgie poo. But the nuclei, the dark and straggle-ended cylinders at the heart of these poos, just didn't match; only a mouse could have deposited those.

Budgie-mice?

My gaze strayed to the ceiling and back to the topmost tiles and I remembered then, and my breath caught in my throat. These turds. No, other turds just like them. I'd seen them before.