A lot of people have the impression that one writes a novel by starting at the beginning and writing straight through to the end. However, this is not necessarily the case. Sometimes writing a novel is rather like building a bridge, working from both banks at once and aiming to meet in the middle.
I'm doing that with Plausible Deniability right now. I've gotten to a sticking point in the early chapters, but I have a strong idea of the ending. So I jumped ahead and wrote those scenes, which simultaneously gave me the sense of progress that comes from having written, and gives me a clearer sense of where the first part of the novel is going. Just having those key scenes written allows me to consider what kind of foreshadowing and element planting I need to do in the early parts of the novel.
So now I'm not only working forward from the beginning, but also working backward from the end, adding the scenes that lead up to the ending scenes I've already written. Hopefully I can bring both ends together in the middle.
Of course if there are problems, there's always the rewrite to take care of them.