I love digging into mysteries like this, so my first instinct is to walk you through the obvious places to check. If the book is a single-author work, the chapter about 'the other side' is most likely written by that same author — usual case. But if the book is an anthology, edited volume, or a collection of essays, that chapter might be by a different contributor and should be credited right in the table of contents or at the top of the chapter itself.
When I hunt for the contributor, I flip to the front matter: table of contents, title page, and the chapter header. Sometimes the byline is tiny or simply a name with an asterisk pointing to a contributors page near the back. Another trick that’s saved me is checking the copyright page and acknowledgments — editors often list who wrote which piece there. If it’s a digital copy, I use the search feature for the chapter title or a unique phrase and scan surrounding lines for a byline or contributor bio. If none of that works, the publisher’s website, Goodreads entry, or even a quick preview on Google Books usually shows chapter authors. Happy to help dig further if you tell me the book’s title — I get oddly excited about little bibliographic puzzles like this.