The annual Halloween block party is the pinnacle of the year on idyllic suburban cul-de-sac Ivy Woods Drive. An influential group of neighborhood moms, known as the Ivy Five, plans the event for months. Except the Ivy Five has been four for a long time. When a new mother moves to town, eager to fit in, the moms see it as an opportunity to make the group whole again. This year’s block party should be the best yet...until the women start receiving anonymous messages threatening to expose the quiet neighborhood’s dark past --- and the lengths they’ve gone to hide it. As secrets seep out and the threats intensify, the Ivy Five must sort the loyal from the disloyal, the good from the bad.

One sultry summer, Maureen Haddaway arrives in the wealthy town of Opal Beach to start her life anew. There, she finds herself lured by the promise of friendship, love, starry skies and wild parties. But Maureen’s new life just might be too good to be true, and before the summer is up, she vanishes. Decades later, when Allison Simpson is offered the opportunity to house-sit in Opal Beach during the off-season, it seems like the perfect chance to begin fresh after a messy divorce. But when she becomes drawn into the mysterious disappearance of a girl 30 years before, Allison realizes the gorgeous homes of Opal Beach hide dark secrets. And the truth of that long-ago summer is not even the most shocking part of all.