Seven years after her little sister drowned in a lake, Kate is finally beginning to heal from Emily's tragic death. Until one night, she spies a familiar face. It's Emily. Kate Hartfield returns to her hometown in the Catskills for the first time since her sister's death, for a work retreat at her boss's lake house. When she sees a girl on the dock next door who looks exactly like Emily, everything she has come to accept as the truth shatters. The girl is all grown up, but Kate knows her sister's face better than anyone. The chilling sighting reignites the doubts Kate has always had about Emily's drowning, and forces her to revisit all the mysterious circumstances that surrounded that day. As she desperately tries to track down the girl she saw on the lake with the help of her hometown ex-boyfriend, Kate discovers shocking secrets from the past, confronts her own guilt from that day, and faces buried demons from her childhood. The more she digs, the more she becomes obsessed with uncovering the answer to one question: What really happened to Emily?