That sentence is, if I am honest, the closest thing I have to a professional philosophy, distilled from forty years of watching people underestimate the wrong person.

The powerful and the confident leave doors open everywhere, because they cannot conceive of a threat from a direction they have deemed beneath them.

The embezzler leaves a trail because he cannot imagine the quiet clerk noticing.

The con artist reuses a phrase because he cannot imagine his marks comparing notes.

And my son left his files flowing into an account his mother controlled, and disconnected only the camera he could see, and forged a signature without checking which version of my name I actually used, all because he had decided, completely, that I was harmless.

The harmlessness he assigned me was not a fact about me.