After spending yet more time away from my novel manuscript to give myself time to think and to come back to it fresh, I began to identify what I felt were some of the biggest flaws with it (thankfully, I don't think there are that many!).
This novel has a fairly large cast of characters. In particular, there are two secondary characters that don't get a lot of time on the page but who nevertheless play an important role in the story. By nature, these characters are a mysterious sort, and neither the other characters nor the reader ever get the full story behind them.
Still, I did realize (and had some folks point out) that I never did specifically call out just what it was these characters did; it's one thing to not reveal exactly who they were or why they were acting as they were, but I least needed to explain what they were doing, if nothing else. It's a complicated story, after all, and leaving a major part of it unexplained (or even if I'd just left it mysteriously implied) just wouldn't work, in this case.
I was worried (as I often am when writing) as to how I would get this information across to the reader--after all, like I said, it's a complicated bit of story, and the nature of this particular aspect still necessitated some mystery, and so I wasn't sure what to do.
The thing about writing, though, which I often forget, is that it's often very easy to get a lot of information across without necessarily having to write a whole lot.
I found a conversation right near the very end of the book. Beyond anything else, I was always a bit 'iffy' on how this conversation went, anyway, because I always thought the characters should be saying more than they did. It made logical sense, in this case, to have them discussing what they'd learned about these two 'mystery' characters, and in just a few sentences, I was able to get the relevant points spelled out in a way that made sense.
While writing these snippets, I realized that there was also one other point that was major and definitely warranted specifically mentioning, but which was also just a single thought that simply needed to be spelled out. Within the same scene I was already working in, I was able to sneak this information in, as well.
In total, the amount of new material I wrote probably amounts to less than a page, but with just those few paragraphs, I've managed to organically cover up what could have been a gaping plothole, tidied up some dangling threads, and even managed to add a touch of intrigue all at the same time.
I am very happy to have done this!