About writing a mystery

I have to admit I was wrong. I thought I had everything mapped out in the contemporary novel I am currently writing and I figured there would be no surprises waiting around the corner for my characters. Well, I should have known better. Sometimes the characters want to go their own way. I'm nearly at 40,000 words right now and don't know exactly where I'm going with the novel. I guess now I have to wait for more inspiration. There is no erotica in this novel, even though there are opportunities for my main character to have a sexual relationship, but I am steadfast with my resolution not to have any explicit sex scenes in this story. Sure, they would fill pages, but it is not about filling pages. I'm happy with what I've written so far, but now I need something surprising, something unexpected. I'm as anxious to discover that as my characters are. Where are you, Lady Muse? Hello...Let's have some ideas here.