Is this ghost story behind the new episode of Sherlock?

Mark Gatiss was hoarse by the time he got to me. The co-writer of Sherlock had flown to New York City to do a round of press interviews before Friday's premiere of a new episode. It's called "The Abominable Bride."

Very little is known about it.

Even though I work in the same building as Masterpiece, the company that distributes the popular show to PBS, they refused give me any clues about what to expect.

Except one simple word: Ghosts.

Ghosts, I thought. Hmm… I wondered. There had to be a supernatural reason behind it.

Had Mark Gatiss seen a ghost?

I put the question to him. And this spooky story, made all the better by his gravely tone, is what he shared…

—

Well…

I did once actually have a supernatural experience. I was very skeptical because I thought it would never happen to someone like me. But it sort of did.

Many years ago, I was living in Leeds. It's in the north of England. A friend of mine went on summer vacation and he let me have his attic room in this big Victorian house for three months. It was a godsend because I was desperately poor. It was a big empty, spooky house.

It started off fine.

But I remember that I went away to Wales and came back and opening the door to this room and there was such a heavy atmosphere inside the room. It was like a hundred people had been in there and as soon as I opened the door they had all jumped out of the window. It was like it was a crowded room. It was so weird. I remember taking a step back. It was strange.

Then all sorts of odd little things started to happen. I had a very strong feeling of being watched.

One night, in the middle of summer, it was so hot that I was sleeping on top of the bed. I suddenly woke up, bolt upright. All the lights were on. The radio was on. And it was so cold in the room that I could see my breath in the air. Again, it was the middle of summer. It was really strange.

I was properly spooked by it.

The next day I rang my friend up. Something in my tone suggested something. He asked if I was OK. I told him I didn't sleep very well. And he said, "Have you seen it yet?"

I said, "What do you mean?"

He said, "I think it might be haunted."

I said, "Yes, I think it might be, too!"

And that was it. He came back and we started to do an investigation. We discovered that the room had a bit of a history. Odd things had happened to people who had lived there before. Someone who had lived on the floor below — when the attic room was empty — used to go up there to study. But had stopped because they felt like someone had been looking at them. All kinds of odd, circumstantial things.

After the summer I moved to Bristol. But my friend rang me up one night. He said, "You'll never believe what's happened."

He had a dinner party. He invited this bloke who people said was slightly psychic. And this bloke asked if he could have a look around the house. Without any warning he wandered up to the top of the stairs to the attic room.

He came back down and said to my friend, "Have you had any odd experiences?"

And my friend, not wanting to give anything away, said, "Well, sort of. Yeah."

The bloke said, "Well, that room at the top, the attic. On the threshold of the door there was someone waiting … 

… and they're still there."

"Sherlock: The Abominable Bride" premieres in the US on MASTERPIECE on PBS at 9 a.m. Friday and at pbs.org/masterpiece