What The Dead Know- Laura Lippman

Not my normal g-pg rated book. This is a little more nasty.
It's about two girls (11 and 15) who went missing 30 years before the story. A woman with no ID turns up leaving the scene of the accident, saying that she is the younger sister and that her older sister, Sunny is dead.
Most of the story follows the original investigation and the years that followed. What happened to the daughters is unclear. All you know is that the woman gives a very detailed description of her sister's resting place, under a specific tree in an orchard. The orchard has long since been dug up and built over no bodies were found. Perhaps she was moved
Then they finally contact the missing girls' mother. As they lead the woman past her she notices a scar where a smallpox vaccine was given. It has the pattern of a fly swatter in it, where her little sister hit her to burst the pustule that formed. The mom immediately id's the woman as her older daughter Sunny.
This is a kind of good story. It's sad because I'm a younger sibling, a younger sister with an older sister in fact so on some counts I very muchly identified with the little sister. (on the failure portion I so id'd with big sis) And she's the one who ended up dead. The older sister's boyfriend killed her (he said it was an accident) and his father (one of the cops that would later investigate the disappearance) hid the body and covered it up by changing the older sister's identity and marrying her off to his son.
Really rather creepy book. The girl, Sunny, grows up to be a really crummy sort of person. I couldn't stand her. I wanted her to jump off a cliff. For 30 years she hid who she was rather than take the consequences of her actions and telling someone who she was and what happened to her baby sister.
My big sister is way better. She lets me bug her all the time and has been known to land me money when I'm broke. Love her. So here's to my big sis. *chugs figurative beer*