Can you put something jangly on the door knob enough to startle him??? I'm having kind of the same problem with Calloway. I can tell he was an indoor/outdoor cat before, and the minute I leave the door unguarded, zoom!!! Out the door he goes, and I live in the city. So, I'm trying to get him to come back down the sidewalks, not go under the cars... sigh. It's frustrating and scary!!! I do have 2 entry way doors, so now I just have to remember to keep one shut before I open the other!!