The double lines on the inspector in panel 3 show that he is a step behind, and trying to catch up with Tracy; who is already ahead of him in more ways then one.
I am also a mechanical engineer, and that is also the first thing I thought of. That is why we are profesional pessimists. Our job is to look for things that could go wrong.
Elly’s hoping that her son is not thinking about it, and Retta is hoping he is.