Dude, you need to set some anti personnel mines. You know trhe ones where you have to dig a hole and place in there. Anyways, seriously you need to set a motion detector wired to the alarms. Oh wait... I got a nice idea.
1. You put something sticky on the door knob or on the ground to keep them there. Kinda like fly paper. I dunno if there is a product out there.
2. Put some wet paint on the ground (or some kind of other substance) in which you can track the "footprints once he/she will step on it. You have to put it where they cannot see it.
3. Put some permanant dye on the door knob. you know those dye bombs when the banks give to the robber to mark the money.
4. Put a trip wire on the ground so when they trip on it they are gonna fall and you will hear them fall.
Personally, I think it is an inside job. I mean when you are not even remotely close to the door knob, you get these gifts. Your wife should lose her "Top Secret" clearance immediately.