When Mary heard this, she fell momentarily silent, as if she were still choosing her words. After a while, she finally spoke.
"Hmm… Let's consider this under the assumption that the main load-bearing structure isn't damaged. Is it possible to realize dynamic connections between spaces in a building by utilizing non-load-bearing redundant areas, like closets between adjacent units?"
The girl asked this with a serious tone. Fields Professor was immediately intrigued.
"Dynamic space connection…," he mused, thinking over Mary's question before answering.
Fields picked up the chalk and pulled down a blank blackboard. The entire lecture hall's attention was on him.
"A very intriguing idea, Miss Morstan," he said as he sketched on the board. "This problem lies beyond the boundaries of conventional structural mechanics. It's more of an architectural trick—a kind of spatial magic, you could say."
Within less than a minute, two adjacent rectangles, just as Mary had sketched in her notebook, appeared on the blackboard.
"Similar designs actually existed in early Victorian architecture, especially in manors built by the aristocracy," he continued. "Their main function wasn't to bear loads, but rather to enable special features. For instance, there might be a rotating bookshelf concealing a passage to a secret room. In other words, the back panels of the wardrobes in two adjacent rooms could be movable, allowing a person to slip from one bedroom to another unnoticed."
As he grew absorbed in his lecture, a fine cloud of chalk dust fell from his gesturing arms. The professor was utterly immersed, forgetting the world around him.
"Of course, those are rather simple magical tricks. But Miss Morstan, what you're proposing is much more sophisticated. Imagine a giant wardrobe: as it slides forward, rather than leaving a void behind, another panel disguised as a wall simultaneously fills that space. The whole process is like a tightly sealed drawer—opening one pushes another in. From the outside, the total volume of the space appears unchanged, but in truth, a passageway has silently opened."
The lecture hall had fallen deathly silent. Most students were completely confused, feeling the professor was unusually excited today and unable to follow his words. Only Russell glanced at Mary's notebook sketch, frowning slightly as he listened.
Professor Fields proposed a technically feasible methodology, but seemed to lack practical application.
While thinking this, Russell stood up again.
"Um, Professor, may I ask a question?"
"Of course, please go ahead, Mr. Watson," Fields set down his pen, regarding Russell expectantly.
"Are there any basic spatial requirements for the design you just described? Say, if the space is split into a living room and bedroom—living room about 10 square meters, bedroom about 9—can this concept still work?"
Fields narrowed his eyes at this.
"10 square meters and 9…," he murmured, pacing back and forth as he began calculating aloud. "Assuming standard masonry, you need at least 240mm thickness for the walls. For a movable structure, add extra mechanical parts and reinforcement—at least 50 centimeters thick."
"That's far too thick. In a small apartment with a total area under 20 square meters, this would make things feel extremely cramped and unreasonable," he explained, muttering technical terms and sketching rapid section diagrams on the board. The once simple blackboard was soon crowded with lines and formulas, becoming a brainstorming ground only Fields himself understood. Most students gave up and became drowsy.
In truth, even Russell couldn't follow anymore. He was simply waiting for a clear verdict from the professor: Yes—or no.
Mary frowned as she softly tapped her pen on her notebook. Too complicated, too costly, too unreasonable, she thought.
"Logically, it is feasible," Fields said at last. "But it's only possible in theory. Realistically, the cost would be considerable."
"I see. Thank you, Professor." Russell nodded and was just about to sit down, when Mary abruptly stood up again.
"What if the existing conditions were doubled?"
"Doubled in size?" Russell echoed, looking back at her.
Fields glanced at Mary and, a bit uncertain, asked, "You mean, actually double the quantity?"
"No, what I mean," Mary shook her head, "is what if, based on the parameters Russell just mentioned, we simply built another identical sample beside it—two side-by-side apartments. Is that feasible, Professor?"
Fields raised an eyebrow, picked up his chalk, turned, and drew the same rectangle once more.
"In that case, I think it is possible," he said. "Mr. Watson, your earlier question boxed in my imagination, confining the concept to a closed system. But what if…." he drew a thick dot between the two boxes, "the system itself was composed of two units?"
"Uh… what do you mean?" Russell blinked, slightly lost.
Could you explain it in a way I'd understand? If not, how am I supposed to explain this to Charlotte when I get back?
"Simply put," Fields cleared his throat and tossed his short chalk stub away, grabbing another, "the concept proposed is theoretically achievable, but the space is just too small for it to be practical. However, if we combine Miss Morstan's suggestion, the original design—meant to be squeezed into just one space—can now be distributed over two. Instead of hiding a passage inside a wall, now the wall itself becomes the passage. We're not just stuffing things into the wall anymore; we're turning the wall into a creative space."
"But… walls aren't hollow," Russell objected.
Fields smiled knowingly, almost as if he'd expected Russell's response. He quickly chalked a rough structural diagram.
"By sliding your side's bookshelf wall, the opposite wall moves in sync, creating just enough room for both people to pass. Once the movement is completed, the gap vanishes and everything returns to normal."
He set down the chalk. "So, instead of saying the wall isn't hollow, it's more accurate to say the visible portion isn't. The actual hollowed-out part is cleverly concealed by the large bookshelf."
…