Later the daughter told me this story: shortly after I left the room, the three of them heard the melodic stroke of a harp. First they blamed one another, believing that one of them had brought a cell phone into the room, but they soon ascertained that there was no phone. Finally they agreed that the sound had come over the loudspeaker, and that it must be our way of announcing that there had been a death.
They later found out from a nurse what I already knew. We don't have a loudspeaker, and the harp sound did not come from us.
I don't offer any explanation for the sound or its source. But whatever it was, and wherever it came from, it made all the difference. The sisters stopped judging one another and themselves for what they had or hadn't done for their mom, the pain of their grief was a little less sharp, and they found themselves laughing at the way, they were convinced, their mom had found a way to reach back to give them one last sign of her love.