“I’m serious,” Lowen said. “Hypothetically, you have this person. She’s a normal person, right? She has normal parents, has a normal childhood, goes to a normal school, gets normal degrees and then goes and has a normal job. And then one day, for no particularly good reason that anyone could see, she goes and murders some guy. And not in a normal way—I mean, not with a gun or a knife or a bat. No, she does it in a complicated way. How does that happen?”

“Is the guy an ex-lover?” Berger asked. “Hypothetically, I mean.”

“Hypothetically, no,” Lowen said. “Hypothetically, the best way to describe their relationship would be work colleagues, and not particularly close ones at that.”

“And she’s not a spy, or a secret agent, or leading a double life as a crafty assassin,” Berger said.

“She’s completely normal, and completely boring,” Lowen said. “Doesn’t even have pets. Hypothetically.”

Berger took a sip from his Cuba libre. “Then I’m going to go with what I know,” he said. “Mental derangement caused by addiction to pharmaceuticals.”

“There are drugs that can turn you from a boring person into a methodical murderer, as opposed to turning them into someone who kills everything in the house in a rage, including the fish?” Lowen asked. “I don’t remember those being touted to me when I was working as a doctor.”

“Well, no, there’s nothing that will do something that specific,” Berger said. “But you know as well as I do that, one, sometimes drug interactions will do funny things—”

“Turn someone into a methodical murderer?” Lowen asked again, incredulously.

“—and two, there are lots of our products out there that will eat your brain if you overuse them, and if they eat your brain, then you’ll start doing uncharacteristic things. Like becoming a methodical murderer, maybe.”

“A reasonable hypothesis,” Lowen said. “But hypothetically this person was not regularly taking either legal or illegal pharmaceuticals. Next.”

“All right,” Berger said, and gave the appearance of thinking quickly. “A tumor.”

“A tumor,” Lowen said.

“Sure, a tumor,” Berger said. “A brain tumor starts growing, hypothetically, and starts pressing on a part of the brain that processes things like knowing what is socially appropriate behavior. As the thing grows, our boring person starts putting her mind to murder.”

“Interesting,” Lowen said. She sipped her drink again.

“I’ve read stories about such things, and not only because my company sells a pharmaceutical treatment for cutting off the blood supply to tumorous masses in the body,” Berger said.

“It’s good to read for recreation,” Lowen said.

“I think so, too,” Berger said.

“And as superficially appealing as that suggestion is, this hypothetical person received a clean bill of health before her last assignment,” Lowen said. “It was hypothetically a job that required extensive amounts of travel, so a thorough physical examination was part of the job protocol.”