He lived alone on the 8th floor in a building next to the park. He had no visitors the day he was killed by a poisoned dart.
(I have a small confession regarding this one. I wrote the twistery puzzles a while ago now. As I wrote each one, I obviously knew what the solution was. In fact, the solution generally comes to me first and I construct the puzzle around it. Now, several months after starting the endeavour, I find that I have forgotten what exactly I had in mind with this one. I think it will come back to me. I’m sure it will!)