Early warning system

Scheherazade has a habit of "pointing" when something catches her interest; she'll stare fixedly at a given spot. When we see her doing that, it usually means that she's tracking a bug, and we'll go over and kill it. (She won't actually kill the bug, but she's capable of following an ant around in fascination for quite a while.) For periods over the past couple days, she's been staring fixedly at a shelving unit in our kitchen. I've taken everything off the relevant shelf (lower right), and tried looking behind it, but haven't seen anything. Well, tonight, she went into full Sphynx mode in front of it, and looked prepared to stay there for a while. This was highly unusual, so I took everything off the shelf again... and discovered that something's been eating our crackers. Huh! Apparently we might have a little furry visitor hiding back there somewhere. I'm going to call the exterminator in the morning, of course, but amusingly, as soon as she saw us focusing on that spot, she wandered away and sat in the hallway looking smug. I thanked her for being a good predator. We'd rather not have a mouse, of course... but I'm very glad that we do have an alert cat on patrol, as otherwise we might not have noticed anything.