How

Everything that Adrian had said, I replayed in my mind.

"The picture that I showed you," Adrian had said, "guess where I took it."

"A park, obviously" Cuthbert had answered.

"The picture is that of a park but I did not take it there. I took it in Brittany's living room. See where I'm headed?"

"Not exactly."

"The CCTV monitoring the apartment building where Angela, the first victim lived, always stopped every twelve hours for a minute to save the video they had recorded. For a full one minute, they went blind. Remember, the clock we found inside Angela's apartment? It was a clue. The only proof that the CCTV monitoring the corridor leading to Angela's and that doctor's apartments was the clock with its moving hands when no one was in the corridor. Remove the clock and no one knows if the CCTV is recording from a picture of the corridor carefully placed in front of it or actually recording the corridor."

"When you put it like that, it sounds as if the doctor is the perpetrator," Peter said.

"She is," Adrian said simply.

"Wait, you're serious? That constantly blabbering nervous wreck is our killer?" Cuthbert asked in disbelief.

"Of course. She had the opportunity to take a picture from the CCTV's perspective every twelve hours for the time she's been living in an apartment. Take the picture without the clock, turn it black and white, print it and when the time comes, place it in front of the CCTV when it goes blind. Last footage of a person recorded by that CCTV was Angela at midnight and the next person was the doctor at three in the afternoon the next day. She had twelve hours, from midnight to noon, to do whatever it was with Angela. Then when the CCTV went blind again at noon, she simply removed the picture."

"That is some planning," Cuthbert remarked.

"The next case," Adrian continued, "the clue was the letter 'B' made in ice just as the clock that formed the letter 'A' with its hands was the clue in the first case. I'm sure you have guessed what was used to kill her."

"Ice," Cuthbert murmured.

"Yes. The heat in the bathroom was on. It was so that the ice would melt quickly, thus effectively removing the evidence and leaving you, the police, wondering where the heck the murder weapon was."

"But how did she lock the door from the inside this time? Even if she used the same trick as the one she used in the fourth case, it seems impossible," I said.

"The fan was on too. And you made the golden discovery yourself," Adrian said.

"The strings?"

"Yes. The strings. Two of them tied around the fan. One connected to the bolt that locked the door and the other to the ice placed above the shower glass. Turn on the fan; it tries to rotate but the weight of the ice pulling on the string keeps it from moving. But when the string holding the ice melts through, the ice falls and crushes the victim's head. Freed, the fan starts moving."

"And the other string attached to the bolt is tugged along after the fan starts moving and locks the door," I concluded.

"See, you're not half bad at this," Adrian said. "Now, the train incident…"

The ping of the elevator as we reached our intended floor snapped me out of my reverie. All of us huddled out and headed for the doctor, Keira's, door. As we walked down the corridor, I looked up at the CCTV. Indeed, paste a picture at a correct focal distance from the camera lens and you would never know the difference.

We reached Keira's door. Adrian knocked on it.

"Who is it?" answered the doctor's shrill voice. Oh, I still remembered her interrogation.

"It's Adrian. The detective who interrogated you yesterday. I'm here with the police. We need to talk."

"Oh, come in! The door is open!"

Adrian opened the door and we all stepped inside. Suddenly, we were bathed in a liquid with a strange smell. Before I knew it, my legs had given away and I had fallen to the floor. So had the others. I tried to get up but my arms and legs did not respond. I suddenly realized that I was paralyzed.

"Wow. I never expected it to work that well and quickly," said a voice. A woman entered my view. It was her. The doctor. In her heavy makeup as usual. But this time, she had a different air about her. She was no longer the hyperactive woman we had met yesterday. She seemed calm and confident.

"Ah, Adrian. The detective who solved my crimes in two days." She knelt down beside his paralyzed body. "We need to talk."