What I really don't get is the leap in logic that the blackmailer could only be Black X. Way to use player knowledge, Editor!
If you can get past that middle tier, I want you to look at the bottom left panel of Archie O'Toole here. That wicked layout is your proof that this is a Will Eisner job. I'm not sure how to map that castle, but I like how the uppermost level is on top of the middle level, sitting in a big box in the middle of the lower level. Or at least, I think that's what I'm looking at!
(Scans courtesy of Digital Comic Museum)