After two days of constant thinking, I decided to visit Mr David Williams. There was not much time left before I had to shift from this place, so I had to at least tell him what I had found. “Hello Steve. So have you made any progress in this case?”, he asked.

“I am sorry Mr David. This case is leading nowhere. I tried to think of every possible combination of incidents which might have occurred but there are always something which proves it wrong. Mark Carter seems the closest one but his behavior doesn't seem like a criminal one…”

I could see a smile on his face which immediately changed after I said, “... That's what you expected me to say Mr David isn't?”
“What are you saying Steve?”
“In this case I just felt there is some character missing from the story. Edward can't commit this crime as he was just very drunk to plan a complex plot like this. Thomas Owen seems innocent because of the evidence his mother collected. And while there is no evidence in favor of Mark, but his behavior didn't feel suspicious to me at all…”

“...I came up with a theory. Let's call this missing character X. So this person X...