From his pocket, Paul drew the flash drive and inserted it into his laptop.

The screen filled with gibberish, as it had the last time he tried it, years before.

His father looked at the screen for a long time.

“Well, your hunch is right. This is indeed encrypted. But how old is this thing?”

“This flash drive is new. But I copied it from an old one, five years ago, and it had been in storage before that. Who knows how long it was there.”

“That explains it . . . This code uses an old version of the Diffie-Hellman algorithm, one that contains an unintentional backdoor.”

“In English, please?”

“It’s encrypted; lucky for us, the encryption was cracked some years ago. Thanks to the leak of NSA hacking tools. As I’m constantly telling you, think of how much better off we’d all be if the NSA didn’t exist. All these government intelligence agencies—”

“Constantly telling me?I haven’t seen you in almost twenty years!”

“Well, I used to—only, you never listened.”

Paul stared at him, infuriated and maddened, all the old feelings returning. He shook his head, sighed with frustration.

“It’s probably hackable using EternalBlue,” his father said.

“Which is?”

“A hacking tool created by the NSA. Leaked by the Shadow Brokers, an infamous group of hackers, seven or eight years ago. The people’s crowbar, they call it.”

“Does that mean you can decrypt this?”

“With the right software and a better computer than this, I could. And my computer science skills are rusty and way out of date.”

“So now what?”

“A student of mine from Caltech teaches at CMU.”

“Carnegie Mellon?”

“Right. He’s brilliant. A genius of mathematical cryptography.”

“That’s codes, right?”

His father gave a skyward glance, nearly rolled his eyes. His standard response to something he considered dopey. “Uh, do you have one of those portable phones?”

*

They spent the night in the seedy motel, each of them exhausted. Paul wondered if he was spending his last night in relative comfort. The next morning, they picked up take-out coffee at a diner and hit the road. It was three and a half hours by car to Pittsburgh, via the PA 28, a boring drive, and for a long time they drove in silence.

Paul found himself thinking that there was something very American about what his father had become. The American isolato had a lot of company, fromWalden Pondto the Westerns. Difficult men intoxicated by their own sense of integrity, cuddly as porcupines and supreme in self-reliance. Americans have always loved the archetype, whether frontiersman or fugitive or Jeremiah Johnson–style mountain man. Easy to heroize. But self-reliance could be self-centeredness, too. A retreat from the ties meant to bind. It took a toll on the people you were supposed to love and nurture. The creed hardened your skin but shrank your soul.

After half an hour, increasingly aware of the tense silence between the two of them, Paul said, “Thank you, by the way.”

“For what?”

“Well, for taking out the bullet.”

“Haven’t had to do that since Vietnam.”

“Huh.”