Well, since we don't have much information about the novel, it's difficult to say precisely. If 'the last one' is about a plot element, it might be the final resolution of a conflict in the story. For example, if it's an adventure novel, it could be the last encounter with the main antagonist. But again, this is all speculation without knowing more about the book.
I'm not sure specifically what 'the last one' refers to without more context from the novel. It could be the last event, the last character introduced, or the last chapter perhaps.
The lack of details makes it hard to give a definite answer. However, if we consider common elements in F Cooper's novels, if it's a historical novel, 'the last one' could be the last historical event depicted. Maybe it's the final battle, or the last decision made by the protagonist that shapes the end of the story. Without having read the specific novel in question, we can only guess based on general knowledge of Cooper's writing style and themes.