And so when I ran through the doors of my own emergency department that night, I already understood, with a doctor’s terrible precision, how close a thing I was about to find.

I understood exactly how narrow the margin had been between my son alive and my son not.

That knowledge is a particular curse of my profession.

Another parent, running into that emergency room, would have been spared the precise medical understanding of how close it had been; they would have had only the general terror.

I had the specifics.

I knew the numbers.

I knew what the officer meant when she said another thirty minutes, knew it not as a figure of speech but as a physiological fact, could see in my mind the exact trajectory his small body had been on and precisely where on that trajectory a stranger’s headlights had found him.