Things That Go Bump in the Night

Leapin' lizards, there's something in our kitchen! It all started with a mysterious bite from an apple, and today it got even weirder. A couple of weeks ago we saw a lone apple sitting on our counter one early morning. It had only one bite taken out of it, and when we asked our oldest son (who loves apples) about it, he said, "Well, I guess I could have sleep-walked and eaten a bite and then forgotten about it..." We decided to remedy the situation by locking the kitchen door at night, and thought nothing more of it.

For a while, all was well. D, who sleeps near the kitchen, felt better about things, and so did I. But then today, she brought us a raw potato with several bites taken out of it. The potato had been removed from the high-up vegetable bin and placed on the counter. The bites from it looked too big to be rat bites, and anyway, our kitchen door had been locked.

If it was our oldest son, looking for an apple in the night--and accidentally getting a potato instead--he would have had to open up the kitchen door in his sleep. But if it wasn't he who ate it, then who or what did? We have considered that it could have been a monkey. But the question remains: how did a monkey get into a locked kitchen??

On the other hand, if it's a rat and it has teeth big enough to make those bite marks, and it's living somewhere in our kitchen, so help me...

What. Could. It. Be?? Somebody give me some helpful hints...