Hours later, Danny returns to his hotel and parks the rental car in the garage. He doesn’t feel very smart at the moment. It’s been a long afternoon, and he knows he screwed up with Carrie earlier. He remembers what it was like when his own father died, and they were never as close as Carrie and her dad.

His first invention was a homemade perpetual-motion generator he made out of Legos and blocks and magnets he found in the playroom. He showed it to his father, who immediately sat down and explained, in great and patient detail, how it would never work in the long term. He showed Danny how the top would eventually wind down, and used this as an illustration of the principle of entropy, as well as inertia, and simpler concepts like the inadvisability of trying to generate electricity with plastic bricks and paper clips.

“Danny, this is really only a toy,” he said. Then he left the room and went back to what he was doing.

Danny was three years old at the time.

This wasn’t anything his dad did on purpose. If he’d bothered to think about it — which he didn’t — he would have said he was treating his son as an equal, that he had faith in Danny’s ability to learn and figure out the answers.

Danny spent most of his time as a child with people who were decades older, who had multiple PhDs, and who usually didn’t have any idea how to talk to children. It was, after all, the way Danny’s father had been raised himself. If anything, Danny had it easier.

Danny learned a lot. He was working on grad-student level problems when most kids were still struggling with the concept of toilet training. He thought he was the slowest person in the room.

He was, however, smart enough to realize that his mother was ill. She spent as much time with him as she could, but she only had a few good hours a day by then. Nobody would tell him what was wrong, so he figured it out on his own after they moved a hospital bed into the downstairs guest room. He looked at the words on the labels of the bottles and the IV bag that hung from the pole, and looked them up in the Physicians’ Desk Reference in the house’s library. Carmustine, Prednisone, Compazine. He looked up the conditions the drugs were supposed to treat, and the answer was easy. His mom had a brain tumor.

In an online database he accessed through Usenet, Danny read the survival rate for the particular kind of brain tumor that his mother had: 27 percent.

That kind of math wasn’t hard. Even if he was a regular kid, he could have figured that out. He wasn’t surprised at all when she died. Not even a little bit.