Pro: You can skip an entire book and the story still makes sense. Con: You can skip an entire book and the story still makes sense. Pro: Birth mom backstory!Con: Introduction of the Devious Four. So evidently, I missed book 3 when I grabbed these from the library, which means I missed the book where Thayer was cleared as a suspect. The twin's birthmother's backstory is explained in this novel, but there is some math that doesn't make sense.