Perhaps I can present my closing argument, and our hosts can strike back at it with whatever reds they please.
A couple of years ago, one of the employees did not participate on his official company holiday. Someone else boarded the cruise in his stead… mystery assassin X.
This poor employee was not left without a cruise, however, as he went on the same cruise at a different time that year.
Mystery assassin X, who had been waiting on the boat for years, finally made his move during the most recent cruise. While he was not present on board at midnight – perhaps he was taking a swim or was on a different boat at the moment – later that night he entered the victim’s room.
As for how he entered the victim’s room, he could’ve stolen a key from someone, or perhaps picked the lock. Or perhaps he had a key of his own that he obtained before the holiday even began.
Inside the victim’s room, he stabbed his unconscious victim in the leg. The victim did not wake up, because he had been injected with a knockout drug that kept him unconscious until after sunrise.
(also, I love the question mark in “A little nugget of anti-mystery [GAME4] [SOLVED?]”)