One of the hundred books a year I read:

Grace McMullen broke up from her boyfriend eight years ago, but decides to check up on him via social media to see how he is doing. To her shock, she discovers he has moved to her hometown, married a woman who looks just like her, and even named their daughter Grace. Creeped out by the similarities, she decided to keep a close eye on him by moving back home.

When she meets the new wife, Grace befriends Campbell who has no idea her connection to her husband. As their friendship grows, Grace suspects her ex is controlling, unstable, and a threat to her new friend, so she decides to save her, but how do you save someone who doesn’t realize they are in danger?

While Grace is watching her ex and his new family, who is watching her?