“You’re right,” Stein admitted. “Altering memories is very risky. Because of the dangers involved, the traditional viewpoint in psychiatry is that you should never do it. You can try to sever the emotional response from the memory, but you shouldn’t try to erase or replace the memory itself. Many therapists and scientists think our life is the product of our varied experiences, good and bad, and that we shouldn’t mess with that.”

“But you’re right, and they’re wrong?” Frost challenged her.

“Not necessarily. I just take a different view. I believe that a patient can decide for himself or herself how they want to be treated. It’s their life, not mine, not anybody else’s. The people who argue against assisted suicide aren’t the ones who have to experience debilitating pain or watch a family member suffer. It’s the same with painful memories. I’d rather empower the patient to live a better life, and if they want to do that by altering part of their past, that’s their choice. After all, a tumor is part of your life experience, too, isn’t it? But we wouldn’t hesitate to surgically remove it. So I don’t think memories are sacrosanct.”

Frost thought about his sister, Katie. All he had left of her was what he remembered. It made him believe that memories were sacred, the good and the bad. Even though there were things that he wished he could forget.

The car in the parking lot at Ocean Beach.

The body in the backseat.

“And how exactly do you alter someone’s memory?” he asked.

“If you talk to my husband, Jason—he’s a neuroscientist—he’ll tell you that someday soon, we’ll be able to use a laser and an MRI machine to light up the synapses in your brain and zap a particular memory. I try to do the same thing therapeutically. It’s a process I’ve spent more than fifteen years honing and perfecting. It combines hypnosis with audiovisual stimuli.”

“And drugs?” Frost asked.

“For some patients, yes, I’ll use drugs to increase susceptibility to hypnotic suggestion.”

“Does it always work?”

“No, of course not. There are no guarantees in psychiatry. My patients sign a release before treatment, because working on the brain is not like working on a car. Sometimes it doesn’t work. Some people can’t let go of memories. In very rare circumstances, treatment can even make it worse—intensifying the emotion or the memory, rather than removing it.”

“Enough that someone might, say, jump off a bridge?” Frost asked.

“If you’re talking about Brynn Lansing, my answer is no. Her treatment was weeks ago. It went fine.”

“So she couldn’t suddenly wake up and imagine herself being attacked by hundreds of feral cats?”