I don't quite understand anything yet, except that the fact that there was no murder can be explained in several ways:
1. Either Shamrock was supposed to kill someone today (by the way, the fact that he was lying under Kaito's door may indicate that he was going to him, or not?), but he didn't have time to kill, because he himself was killed by N.L.
NL leaves no clues
Added 10 minutes later
I would look along the lines suggested by Wolfstet. I don't know, maybe something related to the Dungeon. I've already studied Lodz and Poland, but somehow it's quiet.