“Well, I have a pretty high threshold for horrifying.” Herb chuckled. “You’re talking to someone who once got a ticket for riding a Segway on 101. Anyway, it must be lonely not having them around.”

“I get why they moved,” Frost said. “Too many memories.”

Frost thought about Francesca Stein and realized that everything in life came down to memories. The good. The bad. The real. The imagined. Put them all together, and that was the person you were. Would you ever want to change that? He wondered if his parents would choose to erase that night six years ago if they could. The night he had to tell them about Katie.

“So what’s up, Frost?” Herb asked. “You don’t usually brave the tourist crowds on Saturday morning. I assume that means you need my help.”

“I do,” Frost said.

He often consulted with Herb, because his friend had a pipeline into prominent people around the city and knew most of the street dwellers, too. Herb heard rumors and sucked up secrets like a private detective. He wrote a daily blog about San Francisco life that was required reading for journalists and politicians.

“Dr. Francesca Stein,” Frost went on. “Do you know her?”

“Oh, yes. The master of memory.”

“That’s her.”

“What do you want to know?” Herb asked. “She’s lovely, but there’s steel behind those eyes.”

“Is she legit? The whole memory game sounds like a con to me. Can you really erase a memory from someone’s head? Or create a memory of something that never happened?”

“You think it’s something out of a Michael Crichton novel?”

“Honestly? Yeah.”

“I don’t think so, Frost. The older I get, the more I realize that memory is like one of my sidewalk illusions. It can look very real and be nothing but a fantasy. I remember things that I know are false, and I forget things that I know really happened. I talked to someone who went to Dr. Stein for her memory treatment. One of our esteemed city politicians, actually. He killed a pedestrian as a teenage driver, and it began giving him nightmares years after it happened. Dr. Stein worked with him. He still remembers that the accident happened, but he doesn’t remember it happening. Is that a good thing? I don’t know, but it’s real. And his nightmares are gone.”

“Nobody could make me forget finding Katie’s body.”

“You would think that’s true,” Herb said, “but don’t be so sure. The fact that it’s possible to alter memories is why so many scientists are adamant about our not doing it. They accuse Dr. Stein of opening Pandora’s box. I tend to agree with them, even if I had a fairly fluid sense of reality back in the nineteen sixties.”