“Put on,” Birdie says, softly this time, and Miles Morgan kneels down and places the tie around her neck. He crosses one end over the other, loops it up and over, knots it carefully, and adjusts it so it isn’t too loose or too tight.

Birdie throws herself at Dr. Morgan and hugs him.

Next out of Dr. Morgan’s briefcase is a five-hundred-piece dinosaur puzzle for Nana, free passes to the museum for all of us, and T-shirts that say american museum of natural history on them.

“Thank you, Dr. Morgan.” Nana studies the stegosaurus on the cover of the puzzle box. “I love puzzles, but I never had a dinosaur one.”

“Henry, I brought something special for you.” The curator unzips a small compartment inside the briefcase and passes me a plastic bag.

“This is from my personal collection.”

I lift the bag so the sun coming through the low farmhouse windows shines on the little pebble inside.

I study it through the plastic bag.

“It looks like our rock,” I say.

Dr. Morgan clears his throat and looks into his empty coffee cup. Despite his missing tie, and his shirt having come loose from his pants when he kneeled down to put the tie on Birdie, he still looks very dignified.

“Dr. Morgan, would you like some more coffee?” Nana asks him.

“Certainly, thank you kindly. This was an unusually early morning for me.”

“I’ll get it, Mom,” Dad says. “Save your knees the trip.”

“Why, my knees feel good as new right now! Not a bit of an ache.”

I take the stone out of the bag. It fits in the palm of my hand and looks like a miniature version of the rock in the field. It’s surprisingly heavy for its size, with a single thumbprint-shaped ridge on one side and a few specks of shiny metal. Its fusion crust is black and shiny but flaked away in places, and the underneath rock is gray and pitted.

“It’s heavy for a stone this small,” I say.

“I suspect it contains a high percentage of metal. The Hoba meteorite, for instance, the heaviest one we know, is made up of eighty-four percent iron and sixteen percent nickel.”

Dad leans over the table to get a better look at the stone. I hold it out for Mom to see, too. She strokes it with one finger. I bring the stone up to my nose, but it doesn’t smell like the stone in our field. Maybe the stone lost its smell over the years.

“What else is the stone from your collection made of? And where did you get it?” I ask the curator.

“There you are, Henry. Very good questions. To answer your first question, I believe it contains elements so rare they have not been identified yet. I call it the water rock.”

“What does that mean? None of the rock books in our library have anything about a water rock.”