Madame Frankenstein #5 is on stands this coming Wednesday. It's the crucial part of the middle act. The series is kind of structured in three pieces: issues #1-3, #4-5, and #6-7.
What'cha Reading? has a pretty good overview up until now, free of #5 spoilers, too.
They have a preview, as does the awesome Comicosity site. Or you can just scroll through the gallery below.
I've added the issue to my webstore, as well, in case you wanted to preorder it during this weekend's sale.
Current Soundtrack: Ariana Grande, My Everything