I had that very same thought. It could explain the high number of miles he put on the rental car. Maybe he stashed the body somewhere while on his spontaneous midnight camping trip when he could not figure out all the logistics on burying her - the kids were there, the ground most likely was frozen solid - lots of obstacles to burying a body and hiding evidence. So, he stashed her on a temporary basis. The next day he rents the car, goes back to get Susan's body, places it in the rental car, then drives up to his father's house where he gets assistance. Just speculation on a possible way the situation playe out - I have nothing to suggest this really did happen. But it would explain why the rental car was needed, and why so many miles were put on it. JMHO