My bad: The problem is with the paragraph that starts "His friends called him Tommo." I checked the document and there's only a paragraph symbol above it.

I'm not sure what the instructions "Control+Space" and "Control+Q" are supposed to do--but it changed the font and formatting (no indention) and pushed the phantom line down to above the next paragraph.

Also, the space never appears in the .docx itself, only in the paragraph preview pane (see picture), and when I upload it to the publishers website.