This is the only murder in the series that is done by carbon monoxide poisoning with a car. Usually, this is a method of suicide.
In the introductory scene, the hidden camera takes a picture of Thompson (in a light colored jacket) opening the safe...from the right side of a darkened room. The photo is developed by the photo tech and handed to Thompson. The photo shows Thompson in a dark jacket, almost full-face...in a well-lit space.
The opening scene wall safe combination is Right 80, Left 20, Right 80.