And the trigger for all of it, the thing that had set the machinery of the poisoning in motion, was a message Mark had sent Veronica three days before he drank that coffee, a final, fatal warning: I am handing these invoices over to an external forensic team on Friday. Mark had given her a deadline.

And rather than be exposed, she had decided to make certain that Friday never came for him.

I have thought about the coldness of that decision, and about the ordinary human failing that made Marcus complicit in it, because the two are different and the difference matters.

Veronica’s choice was monstrous: to end a life to protect a theft.

But Marcus’s was the more common, more recognizable failing, the one that any of us might slide toward if we are not careful.

He did not set out to help kill his brother.