Ok. So, I have a theory about the voice that I bet a lot of you guys have already thought of... So. My. Theory. Is. That. Emily & Kevin's dad is actually the voice. In the first book, Emily says that it's like her dad actually lives in an alternate universe, where time moves slower. Kazu is practically telling us right there!!!! There is another point in either book 6 or 7 (sorry, can't Remember which one) where Emily's in her memories, and she saves her dad from the car where he died, but then he tcells her to get revenge on the person who partially caused his death. Then he turns into the voice. So yeah. That's where my theory comes from.