221B Baker Street.
Charlotte, who had been lounging on the sofa, heard the phone ring—something that hadn't happened for a long time. Not many people knew this number. Lestrade was one of them. Mycroft was another. And... Russell Watson was one, too. But since that man should still be in the middle of class at this time, it was unlikely to be him. As for Mycroft...probably not. He was still busy with the Ethan Roy case.
That left only Lestrade. It seemed they'd run into yet another case they couldn't solve.
Pinching the bridge of her nose, Charlotte got up from the sofa and walked over to the phone. But before she could speak, a voice came from the other end. At that moment, she heard a familiar, inappropriate, and incredibly annoying voice.
"Good afternoon. Is this Miss Charlotte Holmes, resident of 221B Baker Street and student at Imperial College London?"
"..."
Charlotte was silent for a moment. She finally spoke, her tone uncharacteristically perplexed. "Why...? Aren't you supposed to be in class at this hour?"
"I skipped for a variety of reasons," Russell replied brightly and cheerfully from the other end.
"So?" Charlotte asked. "Did you call just to boast about that?"
"Aren't you curious where I am?" Russell asked sarcastically.
"I have no interest at all in your plans after playing hooky. If you don't say something meaningful in the next three sentences, I'm hanging up."
"There you go, always in a hurry," Russell feigned exasperation.
"I have two more things to say," Charlotte retorted, picking up her teacup.
"At noon, I spoke with Mary about dynamic spatial connections and gearboxes and whatnot."
"One sentence left," Charlotte reminded him.
"I'm at Holly David's house."
· · ·
There was a brief silence on the other end.
Leaning against the telephone stand, Russell smiled as if he could imagine Charlotte's expression at that very moment. He held the phone with one hand and idly played with a pen on the table with the other.
What was he doing at Holly David's? Charlotte's voice came from the receiver.
"You're not that much of a pervert, are you?"
"That hurts, Charlotte," Russell shrugged. "Didn't I just tell you? At noon, I talked to Mary about dynamic spatial connections."
"Speak like a human being."
"In simple terms, I suspect that the reason ghosts could freely move in and out of David's place was due to some kind of mechanism." Russell explained that he was just recalling his earlier conversation with Mary.
Upon hearing this, Charlotte fell silent, contemplating for a moment.
She then said, "Your conclusion is not much different from what I anticipated."
"Oh? You thought so too?" Russell raised an eyebrow.
"I checked files on that area and found out the apartment had been remodeled," said Charlotte. "To maximize space, the contractors asked an architect to put up a wall dividing a room, allowing them to rent one apartment as two."
"That's a lucrative business," Russell remarked. "Then what?"
"Then, I started thinking about the possible reasons and motives behind the institution's actions. Right when you called. So... what happened?"
"Turns out, you're probably right. I suspect there's a hidden mechanism in the bookshelf in the bedroom." But when he tried to push it, the shelf was too heavy. "So I suspected some trick involving the arrangement of books or something..."
"Don't be ridiculous. That's impossible," Charlotte cut in before Russell finished.
"Why?" Russell asked.
"Holly David put those books there herself. Do you think even she wouldn't know about the mechanism? Then how would a ghost know?"
Charlotte explained. "Besides, you've been looking in the wrong place from the start. The mechanism shouldn't be on your side, but on the other."
"The other side?" Russell was momentarily stunned. "What do you mean?"
"You should have figured this out by now," came Charlotte's voice from the receiver, laden with a hint of helplessness. "Come on, Watson, put that brain of yours—overflowing with lessons and sleep—to use. If you were to install a secret door leading to a neighbor's house, on which side would you put the doorknob?"
"It has to be on my side. I see," Russell answered without hesitation, realizing the meaning as soon as the words left his mouth.
"You should have known this a long time ago," Charlotte chided.
"So, the switch is next door..." Russell murmured to himself. "But I can't just break into someone else's property, can I?"
"If you really wanted to, there's no problem," Charlotte replied. "I'm sure a lonely elderly woman living alone would be grateful if you helped her catch a parasite lurking in her home."
"What if the ghost isn't home and she mistakes me for a thief?"
"Don't worry. I'll go to Scotland Yard to bail you out."
"I don't actually want a criminal record, thanks," Russell rolled his eyes.
In reality, getting into the next apartment wouldn't be hard—one smoke grenade would suffice. The real problem was what to say if someone was actually inside when he arrived. How would he explain? The old lady was about seventy, and if he suddenly conjured up a living person, she might get scared out of her wits. That would be a return to the days of youth.
"Afterward, just politely knock and tell her your intentions. If she agrees, everything will go smoothly."
"What if she refuses?"
"You could remind her that there may be a pervert hiding in her house and, in fact, there's a secret door connecting her apartment with the one next door. For her safety, ask to search the apartment. Even if you don't find the pervert, at least you'll know where the secret door is. So, under what circumstances would she refuse?" Charlotte queried, rebutting his worries.
"Maybe...if she has something to hide?"
"Then, by all means, Watson, go right ahead. Just remember to be polite."
"I shouldn't have to be taught such things," Russell grumbled, ending the call.
He took a deep breath, put down the receiver, turned, and headed for the next apartment.
"Knock, knock, knock..."
A slow, careful knocking sounded on the door.
"I'm coming, just a moment," came the characteristic shuffling steps of the elderly from behind the door.
Russell subconsciously straightened his collar, cleared his throat, abandoned his customary indifference, and put on a harmless smile.
Creak...
The door opened from the inside, revealing the kindly face of the old lady he'd seen yesterday.
"Oh, it's you, young man."
She clearly remembered him and gave him an amiable smile from her clouded but gentle eyes.
"How is that poor girl from last time?"
"Thank you for your concern. She's much better now, and her mood has stabilized," Russell answered gently and politely.
"Good, good," the old lady nodded, almost sighing in relief, "If you need any help, come by anytime, dearie."
"Actually, ma'am," Russell wore a slightly embarrassed, apologetic look at just the right timing, "I'm here today with a small request."
"Oh?" The old lady regarded him curiously. "What is it, dearie? Tell me."
"Here's the thing," Russell launched into his prepared speech. "I study materials science at Imperial College London. Yesterday when I asked my advisor about the situation at your home..."
"Hmm," she listened attentively.
"My advisor thinks this apartment is quite old, and some of the pipes and wiring inside the walls might have aged. At night, the thermal expansion, contraction, or even water flow could cause strange sounds or phenomena."
He paused to observe the old lady. Maybe he was being too elaborate. She seemed confused but a trace of anxiety flickered in her eyes.
"In other words...is this building dangerous?" she asked.
"No, no, don't misunderstand," Russell quickly waved his hands to reassure her. "It's not that serious—just ordinary aging well within safe limits. I'm here today to do a simple check, so you and Ms. David can rest easy."
Upon hearing that explanation, the old lady's expression cleared in understanding.
"I see. Of course, that's no problem," she agreed without hesitation, stepped aside, and opened the door wider.
"Come in, dearie. Is there anything I can do to help?"
"No need, ma'am." Russell breathed a sigh of relief and entered the room. "I can manage. This won't take long."
…