The neighborhood cat came for her usual visit on the evening my friend and I returned from a brief San Diego vacation.  As she bounded through the front door, rather than making her normal fast trip to the kitchen, she paused at the tea cart, placed both front paws on the serving tray, and began to gently bat the lace runner.  Unusual behavior, I mused, until I realized that the lace was moving.  The cat had discovered that a mouse was hiding on the tray.  It had managed to sneak into the house as we were unloading luggage.