The year is 1998, and Lisa Newell and her family have just moved to Oak Valley, the bucolic suburb of the bustling Silicon Valley. Her husband, Michael, is hoping to cash in on the dot-com boom. Lisa is hoping for a fresh start after their marriage has gone through a rough patch. Their daughters are less than pleased by the move, but they find ways to cope. Fifteen-year-old Zoe spends her days locked in her room, chatting online to friends back home, while thirteen-year-old Ashley escapes to summer camp.

With her husband working long hours and her teenage daughters occupied, Lisa joins the local swim and tennis club in an effort to meet people. A tennis clinic leads to a chance encounter with the charismatic and beautiful Simone Culligan, who is clearly the queen bee of the tennis set. Lisa is delighted to be taken under her wing, but soon discovers that tennis isn’t the only recreational activity Simone and her friends engage in. But as Lisa indulges in a second adolescence and participates in her friends' hard-partying lifestyle, she has no idea there is a monster quietly lurking, waiting to tear her family apart.

My name is Madison Culligan. I believe I’m your half-sister.

Having spent the last two decades trying to put her life back together, Ashley Newell wants to keep the past in the past. Now, a message from a stranger threatens to blow her life up once again. But it also may finally lead her to the truth of what happened all those years ago.