I've been wanting to write a trilogy for a while now. From what I've read it's best to write each book as if it were just one complete story. I've been able to do that for most of the first story, but there's a part that really bothers me. I have this character that isn't supposed to appear until the last book, but is casually mentioned and implied to be stalking the main characters throughout the first two books. While he never actually speaks to the main characters in the first book, he does actually save one of their lives. But since he never actually appears in the story, I'm afraid it might come off as too much of a coincidence. Does anyone have any advice, please?