If you haven't returned the loaner car yet, then you have the opportunity of a lifetime. Halloween is a month away and the stores are stocking-up with Halloween stuff. Go to the store and get several tubes of fake blood. Put the blood on the ground just under the trunk and put a little under the car to make it look like the blood is draining out of the trunk. Situate everything to optimize the probability that your wife will see the blood. When she starts asking about it, act nervous and tell her you've go to go somewhere and go to the car and drive away.
