My first mind palace was a pirate ship.

When I was eight years old, my class learned about Cicero. I already knew about him because my mother had read me a book about notable Romans when I was six, and I remembered it. That book, however, did not mention anything about Memory Palaces.

"Your Palace can be anything you like," said Mr. Abbott, his nasal voice becoming interesting to me for once. "And it can be populated by anyone you desire, as long as they remind you of things you might want to remember." I went home that afternoon with an assignment to write down what my memory palace would look like and who might live in it.

"What story shall we have tonight, Brother-Mine?" Mycroft came into my room at eight-thirty sharp. He was never late a moment in his life, I don't believe, including at birth—he was a day early. As a teenager, my brother was no more caring than he is now. He couldn't be; it wouldn't be possible for anyone to care more than Mycroft does. I've always thought that was glaringly obvious, but most people are too stupid to see the obvious facts in front of them.

Using Redbeard as a pillow, I lay across the end of my bed. "Treasure Island," I said, closing my eyes in anticipation of the delicious words washing over me. I loved every bit of Stevenson's tale. I could smell the salty air and feel the tingle of the ocean breeze washing over me.

"Again?" Mycroft pretended to complain, but he didn't really mind.

As my brother's precise voice intoned each syllable, a picture began to form in my mind—a ship, old and wooden, but sturdy, with tall sails flapping in the breeze. My ship. It was grand and tall and imposing as the waves crashed around it.

Mummy would be there for maths—she wrote books about it. Dad would be there for all the extra things, the common sense things, like where Mummy had parked the car outside Tesco when she couldn't remember because she was thinking about Algebraic Equations.

I wasn't sure if I wanted Mycroft in my Mind Palace. A part of me was afraid he would show all of my other memory-people that he was cleverer than me and make them not want to be mine any more. But I couldn't get rid of him, either. He became Latin, something I was just learning. I should have known then that I couldn't get rid of him any more than I could get rid of myself. He's been a permanent fixture in every incarnation of my Memory Palace, like it or not, the archenemy I can't live without.

Mr. Abbott my teacher, appeared on the quarterdeck of my ship, wearing his faded cardigan and round glasses. He represented everything else I might need to remember from school. I blinked and changed him into Mr. Winslow, my teacher from the previous year. I had liked him better. He'd let me read when I finished my work before the other children.

I couldn't think of any other areas to include except the most important one of all—science. I thought then, as I do now, that science was beautiful. It explained the world and music and medicine and why some arguments made sense and others didn't. Cabbages and kings alike could be defined by it. I couldn't think of anyone clever enough—and, to my childish mind, magical enough—to represent science, so I made someone up. I didn't know if I was supposed to do that, but I did it anyway.

Mummy was the cleverest person I knew, and Mummy was a girl, so I thought science should be a girl, too. I didn't much care if she was pretty, but she had long hair, pulled back like I'd seen the lady scientists wear their hair on a school trip to a pharmaceutical laboratory. I couldn't see her face very specifically in my mind, but I knew she was smiling at me.

"Hello, Science," I thought.

"Hello, Sherlock," she answered. "I like your ship."

Even at eight, I knew that science was not really an imaginary friend with long brown hair. But I liked my pirate lady scientist.

Mycroft read three chapters, then shut the well-worn book and set it on my nightstand. "Go to sleep, Sherlock," he said, passing a hand over my hair, which was as curly as his was straight, unlike my body, which was straight and bony where his was curved.

"Good night, Sherlock." Mummy was wearing a blue sock on her right foot and a red sock on her left. She hadn't noticed.

"Sleep well, Son." My father, ever the practical one, brought me a glass of water and leaned over to kiss my forehead. "Redbeard's showing his age," he mumbled as he left the room. I coiled my arms around my best friend's neck and held on tightly. That night, I dreamed I was a pirate with a first mate who twisted her long brown hair into two braids while she told me all about the periodic table of elements.

The next morning, I handed in my mind palace assignment, and Mr. Abbott peered at me over his spectacles. "Science on a pirate ship," he mused. "I often wonder about you, young Holmes."