Eh, I've read enough mysteries to know how this works. Fastolfe's the most obvious suspect, which means he either isn't guilty, or he's so obviously guity that the twist will be that he is guilty.
And when EH opens his PMs, he'll see that Wilson being murdered was my top guess. Fastolfe being dead was second, and the Admiral was third. So, yay me.
(Jan was my dark horse option, and only because I thought the prospect of his being killed would give us some suspects among the PCs, but I considered it unlikely since Jan's "importance," such as it is, was only stepped up as a last-minute decision.)

