Ok, but for most of the book we should make it look like the father/boardmember guy was just selling out his daughter so he could control miniscule aspects of the church... We don't reveal the other plot until later.
AND they fall in love for real as they solve the mystery.
THEN: when they catch him, they eat his heart together.
THEN!!!: they realize that they had it all wrong. That he was only pretending to be controlling the church (as a cover for dumping his waste) so he could foil an alien plot to destroy earth. The aliens were growing a bioweapon on the ranch and the father's team of crack scientists discovered that the only way to stop them was to use this "chemical waste" material--which was really a sythesized anit-weapon for the bio-weapon.
So her dad was a hero, but it's too late. They already ate his heart.
Then they realize that they are brother and sister. They are kind of grossed out, but surprisingly, not that much. After all, they have have both just eaten their innocent (heroic) father's heart.
Also... the organist is a a robot. No one knows this except the ancient church secretary who puts a nickle in the slot every Sunday morning. One Sunday she puts in a canadian nickle. The organist goes haywire and starts singing Ozzy Osborn songs during the sermon. This is foreshadowing for things to come in the second book.
And could there be a talking dog? Or maybe a dog that just knows basic sign language? And if we could find such a dog, could it help us write the book? I've known some dogs that had some pretty good ideas (also some bad ones, but really down to earth).