I was about to leave the apartment building when the neighboring metal door creaked open.

An old lady poked her head through the crack. She waved at me and whispered, "Are you the doctor who's treating Lydia? Is her illness acting up again?"

"Are you familiar with Mrs. Warner, ma'am?" I asked curiously.

"Yes, of course! We've been neighbors for decades, so we're very close. In fact, I watched her son, Jeremy, grow up from a boy to a man. He also always greets me when he sees me.

"They're good people. It's just that Lydia's been getting more and more senile in the last two years. It's honestly a tragedy that she can't even recognize her own husband and son anymore."

My eyes flashed. "Have Mr. Dean and Mr. Jeremy always looked like that?"

"Yes!" the old lady answered without any hesitation. "Their appearances have never changed. The neighbors would definitely notice if their faces changed.

"Lydia has always been a bit of a religious fanatic. Now that she's gotten older, she tells everyone she comes across that her husband and son are monsters. I suspect that she's losing her mind. You can't trust anything that she says, doctor!"

"Did you notice anything different about Mr. Dean's and Mr. Jeremy's habits or behaviors?" I asked.

The old lady frowned as she sifted through her memories.

"Lydia always told us about how Jeremy became terrified of the dark after he fell into an abandoned pit when he was a child. All of us know that he sleeps with a night light. He also keeps the lights in the hallway on throughout the night.

"He stopped turning on the lights in the hallway about a year and a half ago. Sometimes, I would even see him throwing trash in the middle of the night. He's not afraid of the stairwell anymore even though it's pitch-black. In fact, he has no problem at all traversing through the darkness.

"But he's in his 40s now. I suppose that it makes sense that he got over his fear of the dark."

I thanked the old lady for the information and rushed back to the hospital. I then searched the system for Jeremy's records.

Finally, I found an emergency room record that was filed with the pediatric department over three decades ago.

"Patient: Jeremy Warner.

Age: 7 years old.

Diagnosis: Suffered a panic attack and minor injuries after falling into an abandoned pit.

Treatment and Notes: Disinfected and bandaged the wounds. The patient has nyctophobia, which triggered his panic attack."

I mulled over my thoughts.

There was no way that Jeremy and Dean had doppelgangers who were also father and son. If they truly had been replaced, the police would have conducted an investigation after Lydia called them 99 times.

I also ruled out the possibility of Jeremy and Dean getting plastic surgery. Everyone who went under the knife wished to look more attractive and youthful. It didn't make sense for them to get plastic surgery just to look older.

However, I couldn't ignore the fact that Jeremy had nyctophobia. It was odd for him to suddenly conquer his fear when he showed no signs of getting better after decades of treatment.

Furthermore, Lydia was still very lucid. She was able to clearly express her thoughts, so it didn't seem like she was suffering from Alzheimer's disease.

I remained lost in my thoughts for a long time, but I still couldn't figure out what was going on.

Just then, I received a call from Jeremy.

He sounded panicked as he exclaimed, "Mom locked us out of the house, Dr. Simmons! She keeps accusing us of being monsters that want to hurt her. Please help us out.

"She's been acting like a madwoman. I'm worried that she'll kill all of us one day when she actually loses her mind."

I could hear Lydia's cries and curses on the other end of the line.

…

I made it back to the Warner residence about 20 minutes later.

Dean was sitting in the stairwell. His back was hunched, and he kept sighing.

Jeremy was standing by the door. His eyes lit up as if he had seen his savior when he spotted me.

"Hurry and tell Mom that she's going senile, Dr. Simmons. Tell her that she needs to be good and take her medication instead of stirring up trouble for us."

Standing next to Jeremy was a young woman with a slightly protruding stomach. I guessed that she was his wife, Francesca Burton.

I knocked on the door and said, "Mrs. Warner, it's me, Dr. Simmons."

It fell silent on the other side of the door for a moment before there came the sounds of the door being unlocked.

The door creaked open slightly, revealing Lydia's old and wary face. After she was sure that it was me, she swung the door open. She yanked me into the apartment before swiftly slamming the door shut and locking it again.

"Look, Dr. Simmons!" she exclaimed while grinning toothily at me. "The monsters can't get in now! I'll never let them into my house ever again!"

The gleeful expression on her face was reminiscent of a child.

My heart felt heavy as I looked at Lydia.

Confusing one's memories and being unable to recognize one's loved ones were common symptoms of someone suffering from Alzheimer's disease. However, the patient typically wouldn't act so aggressively toward them, even going so far as to think that they would hurt them.

I couldn't help but wonder what on earth was going on with the Warner family.

"Why don't we have a chat, Mrs. Warner?" I asked as I led Lydia to the couch.

Lydia grabbed my arm tightly and said, "I'm not sick, doctor. There's nothing wrong with me."

"I know," I said as I patted her hand soothingly. "Can you tell me why that photo is upside down?"

I pointed at the photo next to the television cabinet. I noticed it during my first visit. The photo frame had been turned upside down and was facing the wall.

It was a bizarre sight, and yet no one in the Warner family had found anything odd about it despite how they were supposed to be a loving and harmonious family.

Fear and confusion flickered in Lydia's eyes. She pointed at the young boy in the photo and said, "There's something wrong with that photo. Jeremy has a small, red birthmark behind his ear, but the boy in the photo doesn't. The birth mark is also missing from the man who's posing at Jeremy.

"The photo must be fake! That's why I turned it around!"

Lydia's accusations were once again based on minute, physical details that outsiders wouldn't take notice of.

I narrowed my eyes. I softened my voice and asked, "Mrs. Warner, when did you first start noticing that something was amiss with your husband and son?"

Lydia's breathing sped up as she exclaimed, "A year ago after the car accident! Both of them were caught in the accident, so they were hospitalized for a few days. After I brought them home, they began looking at me coldly.

"We were together for decades. Why would they look at me as if I were a stranger? Dean's supposed to be my husband, and Jeremy's supposed to be my son. You might not pick up on it, but I did!"

My heart throbbed.

Lydia had constantly insisted that Jeremy's leg was fine, but Dean had mentioned that Jeremy hurt his leg during the accident.

However, at that moment, Lydia had also acknowledged that Jeremy had been involved in an accident.

It seemed that she was indeed confusing her memories. But she was still able to recall many things in great detail, which didn't fit the symptoms of someone suffering from Alzheimer's disease.

I stood up and opened the door, allowing Dean, Jeremy, and Francesca to enter the apartment.

"Mr. Dean and Mr. Jeremy," I said seriously. "After taking into account Mrs. Warner's current mental state and her repeated insistence that things are different than what she remembers, I highly suggest that you take a DNA test.

"After the results are out, she won't be able to accuse you of being impostors regardless of whether she's suffering from Alzheimer's disease."

"A DNA test?" Jeremy asked as an outraged expression crossed his face. "What are you trying to say, Dr. Simmons? Do I have to prove to my own mother that I'm her son? That's ridiculous!"

On the other hand, Lydia seemed to be very much onboard with my suggestion. "I agree! Let's do it!"

Dean sighed heavily before he pulled out a folded document from his coat pocket.

"I've already done a DNA test, Dr. Simmons," Dean said. "Lydia's always been an overthinker. I was worried she would be furious with me if she found out that I had done such a thing, so I had kept it a secret all this time."

I scanned through the report.

The DNA test had been conducted at a third-party organization. The results stated that Lydia and Jeremy were biologically related.

"I'm your son, Mom!" Jeremy exclaimed as he offered the report to Lydia. "I'm not an impostor. Do you believe me now?"

Lydia snatched the report out of Jeremy's hands and scanned her hazy eyes over the words. A bewildered expression crossed her face before it morphed into one of deep fear and hopelessness.

"This is impossible! This can't be!" she exclaimed as she tore the report apart and scattered the pieces everywhere.

"The report must be fake! You're working together to trick me! Monsters! You're monsters who stole my husband's and son's identities! How dare you try to fool me with this useless report!"

She pointed an accusing finger at Dean. "My husband gets nauseous just at the scent of cilantro. You, on the other hand, eat them every meal! And don't try to tell me that you suddenly had a change of heart after not eating them for 70 years!"

She then pointed at Jeremy and exclaimed, "There was nothing wrong with my son's leg! Also, he has a red birthmark behind his ear that you don't have, you monster! You can't fool me! I demand you take another test!"

I instantly tried to soothe Lydia's frazzled feelings. "Okay. Let's just get them to do another test. I have connections with a renowned testing center. I can ask them to expedite the results, so we can get them immediately."

"No!" Jeremy and Dean shouted in unison.

Dean's expression darkened. "I want you to treat my wife so she stops acting like a lunatic, Dr. Simmons. I didn't ask you to come here to cause more trouble!

"A single DNA test can cost up to a few thousand dollars. My family isn't made of money. Doing it once is more than enough. Why do we have to do it again? Unless you believe that we're impostors as well? Perhaps you have some loose screws in your head just like my wife?"

I looked at Dean and said politely, "You're misunderstanding me, Mr. Dean. I also want Mrs. Warner to get better as soon as possible.

"The issue at hand stems from the fact that she strongly believes that you and Mr. Jeremy are impersonating her family members. If she continues living in this constant state of heightened fear, she might end up killing you or herself.

"I'm sure that neither of you want such a tragedy to come to pass, especially since you love her so much. She'll get the answers that she's looking for once and for all if you do another DNA test. Since she doesn't have an issue with Francesca, why don't we ask her to drop by the testing center?"

In the end, Jeremy and Dean agreed with my suggestion.

Dean sighed and waved his hand. "Go ahead, Francesca."

I handed their toothbrushes to Francesca and gave her the address of the testing center.

Franceca's eyes flashed briefly. She looked like she was hesitating for a moment before she quickly composed herself, saying, "I'll head over right now."

I led Lydia, who was still slightly dazed, to the couch and urged her to sit down.

Lydia was trembling all over as she repeated the same things over and over again. "The birthmark… Cilantro… They changed after the accident… They're out to get me…"

Jeremy and Dean sat down at the dining table with somber expressions.