After being hired as a nanny for the summer in the Hamptons village of Herron Mills, Anna Cicconi discovers that she looks like a local girl, Zoe Spanos, who went missing on New Year's Eve. After Anna begins to delve into the mystery, she thinks she knows what happened. When Zoe's body is discovered in a nearby lake, Anna is charged with her murder, but a crime podcaster isn't convinced and sets about seeking the truth.