What my sister had set in motion as a private act of spite had become, without her ever intending it, a federal cybercrime, with her name and her boyfriend’s name attached to it, in writing, on a payment trail no one could argue with.

I had, in the weeks since, done one more quiet thing.

Every threatening voicemail Stephanie left me after the investigation began — and there were several, each one bolder than the last, as though the more confidently she said a cruel thing out loud the safer it became — I had preserved.

She had spent those weeks building the case against herself, believing the whole time that she was building one against me.

All I had to do was keep the receipts.

There is a lesson in that about a certain kind of person, and I learned it thoroughly watching my sister those weeks, and it has served me ever since in a profession that consists largely of watching people build cases against themselves.