Credit: Stuart McLachlan

When I was five, I spilled grape juice on Jiji-san's white carpet. I figured I was in trouble. My grandfather returned from the kitchen with two bowls of miso. He stopped at the red stain and tilted his head, looking at it.

I tried to say, "It was an accident," but I couldn't speak. Jiji-san set the bowls down and said, "You know, David, I've always wanted to paint a carpet. Don't you think that would be fun?" When I nodded, he traced the stain's edge with a finger and said, "What do you think – how about tie-dye?"

So Jiji-san ordered four gallons of concentrated grape and cherry juice from the beverage maker in the kitchen, and we painted the carpet. He taught me the kanji for grape, cherry, and inspiration, in fine calligraphy muddled by the soft fibres.

Then he painted Yukio's name below his case, where Jiji-san had been testing his newest AI developments. We stained the whole place in wild purple patterns. Grandma threw a fit when she got back. Fortunately, my mother arrived to rescue me. Mum laughed when she heard the story – she was used to her father's quirks – but made me swear never to try that at home.

The story made a great commencement speech when I graduated as valedictorian. I talked about Jiji-san's patient math tutoring and how he helped me build my first telescope. He inspired me to study hypertopology at MIT – back when intelligent non-human life was still theoretical – and to join Om-RAC's research department. The world knew him as Taro Nakamura, developer of limited self-replicating AI. But to me, he was my grandfather, who saw the beauty in spilled juice.

When my sister told me that Jiji-san's health was failing, I knew what to do. Despite the crisis at work, I took an afternoon off and headed to Boston. My boss wasn't happy, and I couldn't blame him. I argued with myself on the train ride.

Part of me whispered, "You're supposed to find the Om, this is the chance you've always wanted," but my grandfather mattered more than my career. I could think about work later. I banished equations and data from my mind. It was hard, when I felt so close to the solution. But I'd only have one evening with Jiji-san.

Standing in Jiji-san's house made me feel like a kid again. I looked at the new living room carpet. It had been replaced several times in the last thirty years, although not since Grandma died. Yukio stood in the corner, in a basketball-sized metal case with an open front panel. Chips lay scattered on the nearby desk. Jiji-san and Yukio must have been working this morning.

"Hello, David," Yukio greeted me. "Your grandfather is in the restroom and will be here in a moment." His soothing baritone voice was one Jiji-san had chosen years ago. It reminded me of the weeks my grandfather and I had spent together building simple AIs. This was not the Yukio of my childhood, of course. My grandfather had built the first Yukio, and then taught him to build himself.

"Hi, Yukio," I said, as I hung my hat and coat in the entryway. "How's he been doing? I wanted to visit this summer, but I was so busy with work."

"Understandable. The Om transmissions require a great deal of deciphering and analysis. You are privileged to work on the team responsible for studying hypertopology transport conduits. Your grandfather is very proud of you."

"Thank you."

"Are you still directly involved in the calculations?"

"Yes," I said, which was partly true. I didn't mention my real role, since it was classified. But I had been promoted to a secret team. My job was to use the Om's messages to develop controllable wormhole technology. At this point, we hardly understood what the wormholes were, much less how to use them.

Yukio's words distracted me, making numbers race through my head. I nearly pulled out my handheld companion before I caught myself. I was here for Jiji-san, not work. But somehow I couldn't leave work behind.

My grandfather entered the room, wearing silk pajamas under a robe. He leaned on his cane and rubbed his tangled white hair, looking at something distant. His face brightened when he saw me. "David!" he exclaimed, and dropped his cane.