Most rational people do not believe in ghosts. Why should they? Ghosts don't exist, right?

No. Damn wrong.

Let me start from the beginning. I had been assigned to a murder case where the victim had been killed inside his own shop. The place was equipped with a state-of-the-art CCTV system, so the homicide had actually been recorded on hard disk. The killer hadn't taken the precaution of masking his face, and the camera clearly filmed him while he was carrying out his horrible crime. A good premise for a quick open-and-shut case, right? Wrong again.

I was watching the tape maybe for the tenth time, and I had already printed at least twenty pictures of the murderer in different postures, then fed the killer's close-ups to the facial recognition system, but the result was always the same: the guy on the picture was indeed in the federal crime list, under the serial killers category. Too bad he was already dead, and had been for the last five years.

He had no twin brother, no siblings at all, and he didn't have any relatives we knew of. He was caught six years ago, right after his last murder, but he was killed in prison after only one year of detention.

My captain assigned the case to me, commenting cheerfully: "Constance, you're the only one who can solve this case. You know what they call you, don't you?"

I nodded, unhappily. My fellow officers had started calling me "the mystery detective", after I took on solving the weirdest cases. Little they knew that my unofficial partners, meaning my elemental friends, were actually helping me solve those cases, which were all related to time one way or the other.

But my friends are time agents, not ghost busters, so I really didn't think they could help me in this particular circumstance. That turned out to be my third wrong assumption of the day.

At 10:00 pm I decided that my eyes and my brain needed some much deserved rest, and I headed for the underground garage of the police station. Now, we all know that garages, as a rule, are not very brightly lit, and I can assure you that walking such a scarcely illuminated place at night, right after having repeatedly watched a ghost brutally kill an innocent man, could shatter the confidence of the most down-to-earth skeptic. So I'm sure that you won't blame me for my reaction when I saw a shade come off an especially dark corner; I stopped abruptly and, in the most commonplace horror movie line, I asked aloud: "Who's there?"

I half expected some ugly-looking lunatic brandishing a blood-stained hatchet, but when the figure entered the cone of weak light cast by the wall sconce, the first things that made me relax immediately were the blond, smooth hair and the barely disguised smug grin.

Swallowing a curse and trying to restore a normal heart beat, I said: "Jesus, Steel, you almost gave me a heart attack!"

He said, mockingly: "Jumpy, are we? I can almost hear your heart beating out of your chest from here."

"And I can almost hear the shot that was about to go off my gun." I retorted curtly, showing him my armed hand.

He half raised his hands in mock surrender, his grey eyes shining impishly. He said: "You won't need that in your next assignment."

Taken aback, I asked: "You mean this case is operators' material? You deal with ghosts, too?"

A female voice from behind me caused my heartbeat to quicken again. Will I ever learn?

"We do, as long as they are afterimages created by time."

I turned round abruptly, facing the ever composed Sapphire, and asked, out of breath: "Why do you always appear in different places? That doesn't help, you know?"

She just beamed her serene smile at me and didn't bother to answer.

Steel said: "Can we go to your place and talk? I think this garage is somehow disturbing your peace of mind."

I retorted: "It's downright creepy, that's what it is. All right, I'll give you a lift to my apartment."

For once, I saw a brief flash of dread in his usually impassive eyes, and I suddenly remembered that Steel hated cars in general, and my driving in particular.

Vengefully, I asked: "Jumpy, are we?"

He just glared at me, and Sapphire said, failing to hide an amused grin: "I think we'd better meet you there."

Twenty minutes later we were all sitting in my cramped living room, where I felt much more at ease.

One thing that Sapphire said earlier was nagging at me, so I asked her: "You mentioned something about an afterimage."

She said: "That's right, yes. You would call it a ghost."

"Then tell me something: how can this afterimage of yours brandish a knife and viciously inflict thirty stab wounds on a poor fellow's torso?"

She briefly closed her eyes, probably stricken by the violence of the image. But she immediately regained her usual placid expression.

"The difference between an afterimage and a ghost is that the former is a materialization of somebody who lived in the past, whereas the latter… doesn't exist."

"Ghosts don't exist?"

It was Steel who answered me with another question: "Are you disappointed?"

"No, it's just that… well, you're sort of debunking an old myth. Now I won't be able to enjoy all those ghost stories in front of a campfire anymore."

"Believe me, this assignment will more than compensate that loss."

"Tell me more about it. What do you know of this afterimage?"

"Time is using that killer's thirst for revenge as a source of energy to materialize him in the real world. The man he killed was the one who allowed the police to apprehend him."

I was stunned. "Why wasn't that information included in his file?"

"Because the police didn't know about it. You see, five years ago, the man that was killed last night saw the killer enter his last victim's house while he was driving in front of it, heading home. He did call the police, but he used a public phone and did not disclose his personal data."

I nodded; the report did mention an anonymous call to 911.

"So that proves that it was really him: only the killer knew that detail." I said.

"Precisely."

Now I was thinking aloud. "But if this killer wants revenge, he's going to murder all the people involved with his case."

Steel said: "That's highly possible, yes."

I darted from my armchair, reaching for my phone. "Then I'm sure that the next thing he will do is go after the man who killed him in prison, and probably also the judge who sentenced him. I'd better make a couple of very urgent phone calls and warn these people."

Less than five minutes later I had already discovered that the first potential victim I mentioned was already dead, killed a few hours earlier by thirty stabs to his torso, presumably by one of his fellow conmen. Only I knew that the culprit was my dead killer. Not only he used the same weapon, but he also inflicted the same number of wounds. The connection was easy enough to make: it was the same number of years of prison he was sentenced to.

Now it was the judge's turn. I had to pull a few strings, but I finally got his cell phone number. When I called that number, though, a relative answered me, explaining that the judge had just died of a heart attack. When I asked him if the judge had a heart condition, he told me that he was healthy as a horse, and that, according to the doctor, it looked like something literally scared him to death.

When I put the telephone down, I probably was a shade paler than usual, because my friends asked me what happened. I told them about the killer's last two victims.

I remarked: "Probably the judge went into cardiac arrest when he saw a dead man threatening his life. He was healthy, but he also was 75 years old. The killer didn't even need to stab him."

Steel asked: "We must stop this chain of murders. Who else could be in danger?"

I counted on the tips of my fingers. "The police officers that arrested him, the prosecuting attorney and, last but not least, the man he was planning to kill when he was arrested. He might want to settle that score, too."

"Find their phone numbers and call them up to warn them. In the meantime, we will pay them a visit, one by one. If we're lucky, we will bump into the killer."

Steel and I decidedly didn't share the same concept of luck.

This time my friends didn't have a choice, and they were forced to get in the car with me. I found out that when they didn't know where their destination was, they couldn't teleport there, unless they were given the exact coordinates by someone like their Authority.

Steel's distaste for my driving was aggravated by the fact that I was calling up the potential victims to warn them and to inquire on their whereabouts.

The situation was too serious to joke about it; I actually felt a bit sorry for him, and I felt the need to apologize.

"I'm sorry, Steel, but I need to go as fast as I can."

Grabbing the armrest with a vice-like grip that probably left dents in the material, he said: "No need to apologize, detective. As much as I dislike your driving, I realize the urgency. Do carry on."

Despite his brave words, he was unable to hide the slightly green hue on his face, and I fleetingly wondered if elements could actually throw up. As far as I knew, they take human form to work among humans, so they are supposedly equipped with all the necessary organs, but they don't eat either, so it was really hard to tell. I made a mental note to ask Sapphire in a less pressing circumstance.

When we came to a screeching halt in front of a rather desolate warehouse, Sapphire asked: "What are we doing here?"

I explained: "This is where the second police officer that arrested the killer is supposed to work. He retired from the police two years ago and became a security guard. He should be on duty right now. Let's go."

I grabbed my gun and got out of the car. I had already taken the precaution of wearing my bullet-proof vest. Maybe it wasn't effective against ghosts, but as sure as hell it was against knives.

I tried ringing the bell a few times, but when nobody answered I decided to break in. I was about to pick the door lock, when Steel said: "Allow me."

I moved aside and watched while he palmed the door over the lock and slowly turned his hand counter-clockwise. I heard a click, and the door inched open.

I said, impressed: "Wow. Very handy."

Without answering, he preceded us inside, turning on the lights. The first rooms were offices. We found the guards' control room, but the former police officer was nowhere to be seen. I had a very bad feeling about that, so I started searching the premises in search of what I now was pretty sure was another man knifed to death. We decided to split up to carry out a more efficient search, but I must confess that I regretted that decision almost instantly. The place was spooky, poorly lit and consisting of countless lines of crates, the perfect hiding place for anyone who wanted to successfully ambush an unsuspecting victim-to-be. True, I was everything but unsuspecting, but I could still become a victim at any moment.

What contributed to soothe my nervousness were the soft voices of Sapphire and Steel exchanging mental communications.

For some reason, I can hear them in my mind, as I found out the very first day I met them.

Now they were checking on each other's position, and that also helped me take my bearings in that maze.

But suddenly I realized could not hear Steel's voice anymore. I did hear Sapphire calling him, though, her voice growing more and more concerned by the minute.

If she wasn't able to reach him, I certainly didn't have any chance at succeeding, so I didn't even try, and resolved to rely on my police instincts instead.

After a few minutes, those same instincts made all the hairs on the nape of my neck stand up. I slowly turned, ready to fire my gun, but I relaxed immediately: Steel was standing there.

I said, relieved: "Steel. We couldn't hear you anymore, and we were worried. Did you find anything?"

Nodding, he got closer, but he didn't say a word. I was somewhat taken aback, but not alarmed, so I didn't move when he raised his hand as if to touch me.

But suddenly Sapphire's voice made Steel jerk his hand away: "Stay away from him, detective."

I was dumbfounded. "What's the matter, Sapphire? It's only Steel."

She said, her voice deadly serious: "No, it's not."

I didn't have time to ask for an explanation, because at that moment all hell broke loose. Steel growled ferally and flung himself at his partner, hitting her face hard with the back of his hand. Sapphire was knocked unconscious by that vicious blow.

Despite the astonishment, I reacted immediately and threw myself at Steel, trying to protect the poor Sapphire from any further damage.

I knew that Steel had an outstanding strength and that I had no chances of subduing him without using my gun, but I really didn't feel like shooting my friend. That soon turned out to be a big mistake.

We struggled. Or rather, I struggled, employing all the martial art moves I knew, while Steel just resisted my blows as if I were a little kid playing with her dad. But soon he grew tired of my pathetic attempts, and he aimed a powerful blow at my head. I saw it coming and moved my head out of the way, but his fist impacted against my right collarbone, and I heard a loud crack. By experience I knew that that kind of fracture is quite incapacitating, so I really didn't stand a chance when he grabbed me by my shoulders - painfully aggravating my freshly broken collarbone - and viciously propelled me against the wall with the force of a cyclone.

My bullet-proof vest somewhat dampened the blow, but the impact was still hard enough to crack a few ribs. The pain was searing, and my eyes filled with bright spots of light.

I was still conscious, though, and I saw Steel approaching me with a cold, murderous look in the thunderous grey eyes. But I also saw something else; a uniformed man coming out from behind one of the crates, aiming his gun at Steel and firing repeatedly.

I yelled: "NOOOO!", but my scream was drowned out by the deafening detonations. The man fired the whole charger at Steel, but I lost consciousness well before the last bullet was shot, while my eyes recorded the image of Steel collapsing, deadly red flowers blossoming on his chest.