Gabriel did not make promises like that.

When Gabriel told my sister something, she could build her whole day on it, and she did, and she was never once let down.

I nodded along, my chest warm with a feeling I could not yet name, and I filed the moment away, not knowing that a promise made on a gravel playground would turn out to be the first visible thread of something far larger and far more selfless than any of us could have imagined.

I think often about the word promise, because it turns out to be the load-bearing word of this whole story, the thread that runs through all of it from that playground to the hospital.