“This writing is my only way of thinking,” Zasetsky wrote. “If I shut these notebooks, give it up, I’ll be right back in the desert, in that ‘know-nothing’ world of emptiness and amnesia.”

After his lecture, in response to a question, Hiroji described the work he had done on the Thai — Cambodian border in the late 1970s, in the refugee camps. He went, he said, because his brother had been a part of the Red Cross humanitarian mission in Phnom Penh, Cambodia, during the years of the Vietnam War.

As the students filed out, I approached him. Awkwardly, I planted myself in his path as he made his way up the steep steps of the lecture hall.

He looked at me inquiringly.

“Excuse me, Professor,” I said, staring at his shoulder. “Could I ask you, your brother, the one you mentioned, could I ask if he has returned to Cambodia and how he has found it there, for the people, and what is Phnom Penh like? This is something I’ve been wondering. Have they repaired the buildings and are people able to return to their former homes? Can you tell me, please, what the city is like?”

He stared at me, as if trying to translate my words into another, more decipherable, language.

“Oh,” he said at last. “But he didn’t

come home.”

I stared harder at his shoulder.

“What I mean is,” Hiroji said, “my brother is still missing. James disappeared. In 1975.”

“Oh,” I said, blushing. “I see.”

“But I went there. I went to Phnom Penh.”

When I met his eyes, it seemed he was about to ask me something in return but I backed away from him, turned, and ran away up the stairs. The teaching assistant, standing beside Hiroji, called my name but I kept going.

Years later, when I met Hiroji again at the brc, he still remembered this encounter. We were in my lab, the computer crunching its way through layers of statistical analysis, when he reminded me of it. I asked Hiroji to tell me about the border camps and the boy, Nuong, he had grown close to.

By then, something in me was changing. My brother was returning to me, so finely, so clearly, just as he had been at the end. I wanted to keep him near to me and yet, I told Hiroji, I couldn’t live with this memory. There was nothing about his last moments that I could change.

Beside us, my computer scrolled through data, pulsing signals.

For hours we talked, roaming together, stopping at the wide branches of Gödel and Luria, the winter stillness of Heisenberg, the exactitude of Ramón y Cajal. He told me about memory theatres, how the Italian philosopher Camillo constructed his own in the seventeenth century. His theatre was a room filled with ornaments and images, inside a structure that he believed echoed the layout of the universe. Standing in this room, one could be simultaneously in the present and within the timelines of the past. Bopha’s imaginary book came back to me, but now her book was something that I could enter. The pages would remain, like a library, like a city, holding the things I needed to keep but that I could not live with. If such a library, a memory theatre, existed, I could be both who I was and who I had come to be. I could be a mother and a daughter, a separated child, an adult with dreams of my own. These ideas, these metaphors and possibilities, were the gifts Hiroji gave me.

Once, I asked him, “Why are you so kind to me?”

Hiroji had looked at me with a gentleness that I will always remember. “Because you’re my friend, Janie. Because a friend can do no more.”

The doors of the metro clank open. This is my stop. We go up and up to the world above. On the sidewalk, snowplows come, flashing lights, slowing traffic.

Sunlight angles off the snow, blinding everyone.

On the fourth floor of the brc, I go to Morrin’s office. When he looks up, his eyes register surprise. I comb my fingers through my hair and tell him that I was delayed this morning. “Janie,” he says, focusing on me. “Do you want to come in and talk? I’ve been thinking about you since —”

Alarmed, I step backwards. I ask if the talk can wait, I have some work to finish. He nods. The door rattles as I pull it closed.

Outside the door to my lab, I telephone Navin. When I apologize for not seeing them this morning, he says, “Why don’t we visit you in the lab? I was planning to take Kiri downtown.” I falter for a moment and then agree. “We’ll be there around six,” Navin says before hanging up.

Inside, silence reigns. When I turn on the rig, my hands are damp, from warmth or perhaps nervousness, but slowly I lose myself in work. This room, deep in the basement, is where we electrophysiologists barricade ourselves from the dancing robots, fizz-bang experiments, and jumbo scanners of the more flamboyant researchers.

When Navin and Kiri arrive, the laboratory has emptied. I am the last one, still trying to catch up.

“Momma, we’re here,” my son says. “We’re here.”

I take him in my arms. Navin is holding Kiri’s discarded hat and mittens. They bubble, ripe with colour, from his pockets.

“You’re warm,” Kiri says. “See how warm you are.

“We walked all the way from Côte-des-Neiges,” he says proudly. “Down the big hill and then we saw a hawk but it didn’t come too close.” Unzipping his coat, he goes directly to the Zeiss. He looks into the microscope, studies the slide for a moment, and lapses into a contemplative silence. The first time my son came here, he was four years old. He had gazed at a neuron, lithe as a starburst, stained Nile blue. My son knows about pipettes and single-unit recording, he knows that there are neurons and also glia, that Aplysia is a kind of marine snail, and that the brain, full of currents and chemistry, is never at rest.

Navin goes from microscope to microscope, peering down, in case one of my colleagues has left a slide behind, a bit of hippocampus.

I go to him and touch his elbow. One of his arms folds over me like a wing. I tell him, “I’m glad you came.”

From his pocket he takes out a small, porcelain owl. “We saw this on the way and thought of you.” In my hand it feels like a polished stone, hollowed out, alive and perfect.

“Ma,” Kiri calls. “Come look. Aplysia.”

I go to him and put my eyes to the lens. Kiri rests his fingertips against my hip.

Bit by bit, one micromillimetre at a time, I lower the tip of a glass electrode toward the neuron. My head feels heavy, but somehow the pipette glides with stoic precision. Anaesthetized, pinned flat, cut open with surgical scissors, this innocent creature and her brethren have given me more cells than I dare count. I feel as if I can operate on Aplysia blindfolded: first, removing a tangle of nerves, then, carefully, delicately, extracting a particular neuron and its spindly axon, the axon sagging out like fishing line. Aplysia was the first creature I studied long ago, in Vancouver. In the sea, she looks like a petal swirling through the water, her gills clapping softly together.

When the electrode is touching the cellular fluid, I increase the voltage, waiting, hand on the dial of the amplifier, until the neuron fires. Here it comes: my signal amp is connected to a speaker, so we can hear the cell itself. Boom. Boom. It sounds like artillery fire, like a parade.

This is Kiri’s favourite part. “What’s he saying?” my son asks.

I close my eyes, listening. “He’s saying, ‘Open the door, let me in! I have a message!’”

“Come in, come in,” Kiri whispers. “Tell me.”

My son’s lashes, long and frail, are like tiny wingtips. I kneel down, touching his shoulders. They seem frighteningly small, weightless.

“Where does a thought come from, Momma?”

“From what we see. From the world inside us.”

He considers this. “Can you make a thought?” he asks. “Can you grow one in a dish?”

“Soon we’ll grow everything in dishes,” Navin says.