Cat flap

In the past year we have had two cats slip out of this house, and one cat slip in.

The first one was Peaches, who managed to get out of the house and wound up perched on top of the air conditioner, crying. My mom was able to pick her up and bring her in.

A few weeks (or months) later, I don't remember, one of our neighbor's cats got out of her house. We looked and looked, but he was nowhere to be found, at least not in any of the spots he has hidden when he has gotten out in the past. A week later, while cleaning the litter boxes in the basement, I spotted a cat watching me from the rafters. I was taken aback because he wasn't anyone I recognized. I was able to catch him - a big, well-fed, docile cat - and we identified him as our neighbor's missing cat. I carried him back over to her house, and he hasn't run away since.

Yesterday my brother and his sons were over to do some shrub pruning, and they found a groundhog hole alongside the house. Before I went to work I grabbed a shovel and filled in the hole using the displaced dirt piled up in the garden. Then I set up my Havahart trap, baited with an apple.

Midday today the trap was sprung. But the apple had been tossed out of the trap. Inside the trap was our most recent acquisition: Spooky, the little black cat we took in in January.

How did he get out? Maybe when I took the trap out yesterday? Maybe when my mom got the paper this morning?

How did Peaches get out? How did our neighbor's cat get it?

I checked all the basement windows and they are secure. I don't think there are any secret passages into and out of the house, or this sort of thing might be happening all the time. So what is going on?