But the dowsing rod is tugging. At the very back of the visitors’ center, under a few streams of pitiful light, I find a room that looks more like a historical society than anything else, with little exhibits and large stacks of binders and record books. There’s a display about the worst flood on the Eel River, the one that washed away a whole town. Prospero, California, according to copies of articles about the flood sitting under shiny glass. There are tiles from the roofs of houses that people ran up and stood on when the floodwaters rose. There are pictures of the rooftops, small unnatural islands in the swirl of water.

“Did you know about this?” I ask.

Rush nods in a vague way. “Everybody knows about the flood.”

I turn from the exhibit to the record books. I slide the dowsing rod over the stacks, and everything feels smooth and normal and there’s nothing strange here, nothing worth a second look.

Then I feel a snag, like a stitch that doesn’t line up with the others.

I slip the dowsing rod back into its case and pick up the brown leather book that caught the rod’s attention. The book feels good in my hands, perfectly weighted and solemnly right, so I turn back the cover. It opens clean in my hands, like someone cracked the spine to a certain page a long time ago.

It’s from the year of the Eel River flood: 1926. Most of the page is taken up by pictures of the relief efforts. The bodies of houses washed up far down the river, wrecked on the shores. My eyes keep moving until they reach a tiny paragraph at the bottom.

A young woman was declared missing: Emma Hart, daughter of James and Laura Hart, engaged to Robert Mason. She disappeared shortly after the flood, after the waters stopped rising. It was believed she ran off into the woods. There’s no reason given, no source for the strange certainty, when she just as easily could have fallen into the still-high waters of the river. That’s the whole story. Next to it is a picture, clearly taken before they started telling everyone Smile for the camera.

Robert Mason has a face that I’ve forgotten before my eyes have traveled all the way across it. But Emma — Emma has a hurricane of dark hair and a stiff white shirt. Her body fights the tightness of her blouse. The color of her eyes is impossible to tell, but they stare through the thin yellow paper, through the years between us that suddenly feel thin, too.

She looks at me the way the Grays do. Like I might save the world or I might be a complete disappointment.

Emma and Imogen: The Past Ninety Years