I’m a single sculler—a rower who uses a one-person boat—so I’m used to being alone and looking backward. Most of the time, my backward glance allows me to take in scenery that, after fifteen years on the Charles, I know by heart: the dense brush along the upper reaches of the river; the half-submerged shopping cart by the first bridge; the purple graffiti on the embankment of the sixth, its giant letters shouting I’M SORRY. But sometimes the view surprises. And just once, the view pulled me into an event as extreme as that graffitied apology, and almost as mysterious.
