Since I don't feel like wading into the debate about Kanon, I'll just drop off something else I spotted in EP3. This conversation takes place right after the 2nd twilight is discovered, and the adults are discussing the possibility that the 1st twilight was faked.
Spoiler for EP3 dialogue:
Nanjo: "............My apologies, ......but that is not so. ...I am quite old. There may be a chance that I made a misdiagnosis. ......However, I would never mistake whether they were alive or dead..."
Rudolf: "......In that case, it's more natural to think that there's someone hiding around who's acquainted with the mansion, carrying out a well-polished crime. In other words, from the time that the typhoon came to this island and sealed it off from the outside world, there were more than 18 people on this island."
Kyrie: "Maybe it's fairly consistent if you think of it that way. ......In other words, this person who's hiding is actually someone who shouldn't be on this island right now. And yet, there's the possibility that it was someone whose face was known by Rosa-san, and with whom she would let her guard down."
Natsuhi: "......S, so, for example, could it be, a servant whose shift doesn't lie on these two days...?"
Krauss: "Hmm.........It's hard to argue with that one. When they finished their service and left the island, it isn't as though we made sure by punching their ticket or anything. If we suppose that a servant on a shift from a few days ago only pretended to leave the island, and actually stayed here, that would be hard to deny..."
Hideyoshi: "...I don't think Rosa-san is such a fool. If a servant who was supposed to be dead popped up in front of you, any normal person'd be at their most cautious..."
EDIT: Never mind, this appears to be a translation error. I thought I had the most recent version of the translation, but I guess not?