I arrived in Trieste on a Tuesday in March.

I had not slept on the flight. I had not slept the night before it. I had the twelve clues memorized by then — I had worked through them so many times over four years that the answer felt less like a discovery and more like a confirmation of something I had always suspected without being able to name it.

Trieste. A city that had spent decades belonging to no one. A city at the edge of the map, facing a gulf with its own name, built on limestone that goes all the way down to the sea. I had never been. I understood immediately, standing outside the airport with my bag, why he had chosen it. It is the kind of city that keeps secrets without trying.

I did not go to the police first. I know how that conversation goes. Four years, ten murders, no physical evidence linking a single suspect — a retired detective with a postcard and a theory is not something any force moves quickly on. I needed to find him first. Or find her.

I had a name. Not his — I still do not have his name, not his real one. But I had enough from the case files. The pattern of how he found them. The conferences, the lectures, the cycling groups, the professional events. Whoever she was in Trieste, she was in her early forties, dark-haired, pale-skinned, with a particular quality around the eyes that I had seen in ten photographs taken at ten different crime scenes. He finds women who look like the woman in the photograph. He has been doing this for ten years and he has never stopped because no one has made him stop.

I spent the first day walking. I know that sounds like nothing. But cities tell you things if you walk them slowly enough and I have been doing this long enough to trust what they tell me.

Trieste is a small city. It has a square that opens directly onto the gulf — the largest seafront square in Europe, which sounds like a boast but is simply a fact. It has a wind called the Bora that comes off the Karst plateau in winter with enough force that the city has iron handrails embedded in the pavements. It has limestone caves in the hills behind it that go on for kilometres. It has a neighbourhood of Habsburg architecture that looks like Vienna transplanted to the Adriatic. James Joyce lived here for eleven years and wrote much of Ulysses in a city that barely remembers him now.

It is a city full of things that should be famous and are not. He would have loved it for that reason.

On the second day I found her.

I am not going to write her name here. She has asked me not to. What I will tell you is that she is forty-two years old, dark-haired, pale-skinned, a marine biologist at one of the international research institutes that cluster around Trieste — it has more researchers per square kilometre than almost anywhere else in Europe, something to do with the cold, clear water of the gulf and a century of scientific tradition.

She had met a man at a conference in Ljubljana four months earlier. He was charming, curious, attentive. He had mentioned Trieste — described it with a kind of precise affection that she found unusual in someone she had only just met. He knew the caves. He knew the square. He knew the wind by name.

She had not heard from him since the conference. She did not know his name was not the name he had given her.

I found her through the institute. I told her enough of the truth to make her take me seriously, which took longer than I would have liked. I showed her the photograph — the one from the third crime scene, the unidentified woman. She looked at it for a long time.

She said, 'I don’t know who that is.'

I said, 'Neither do I.'

She said she looks like me.

I said, 'Yes.' That’s why I’m here.

We went to the police together. This time the conversation went differently — partly because she was there, partly because I had four years of documented evidence in a file that I had carried onto the plane in my hand luggage because I was not willing to put it in the hold, and partly because the officer we spoke to had heard of the Postcard Killer and had a sister in Edinburgh and took the whole thing more seriously than I had expected.

He was already gone.

He had left Trieste nine days before I arrived. The apartment he had rented under a false name was empty and clean. He never leaves anything. I have known this for four years. I did not expect him to start now.

But he had.

On the kitchen counter — bare except for a single item placed in the center, with the deliberateness I have come to recognize — was a postcard. Blank on the front.

No city. No image.

I turned it over.

On the back, in his handwriting, one line:

“You are getting warmer, Marcel.”

And beneath it, in the same neat hand, a name. Not his name — I am certain of that. But a name I did not recognize. A woman’s name. A city I had not yet considered.

I have considered it now.

The photograph. I said I would tell you about the photograph — the one recovered from the third crime scene, never identified, the woman who looks like every victim in this file.

Her name is Anna Reiter. She was thirty-four years old when the photograph was taken, a musician from Salzburg, reported missing in the spring of 2009 and never found. I identified her three days after I returned from Trieste, cross-referencing the photograph against missing persons databases I should have searched four years ago and did not because I was looking in the wrong countries.

I do not yet know what she means to him. I do not yet know whether she is alive. I know that she is the reason all of this began — I am as certain of that as I have been certain of anything in this case. I know that whatever happened to her, or whatever he did to her, or whatever he witnessed, set something in motion that has now killed ten women across ten years.

I am going to find out what it was.

He left me a name. He left me a city. He believes he is still ahead of me. He has been ahead of me for four years.

He will not be ahead of me for much longer.

Marcel Voss

Paris

The next case is already open.

The name he left. The city he pointed to. What happened to Anna Reiter in the spring of 2009.

You will be the first to know when it is ready.

You are already on the list.