I have questions

[An]

I just finished Under Lock And Skeleton Key by Gigi Pandian. I know the book was released about 3 years ago, but I have questions. Any new or old readers care to join in on a discussion?

[An]

I have a question about (view spoiler)[ the murder, the discovery of the body, and the 'solution' offered near the end of the book. It is repeated many times that there was no way to put a dead body into the sealed wall, and the solution was the body that was found in the wall was actually just a dummy and it was switched after. So my question is, then how did the killer put the dummy into the sealed wall? Did I miss something. (hide spoiler)]