A six-year-old girl sneaks out of bed to capture a mermaid but instead discovers a dead body. Terrified and unable to make sense of what she sees, she locks the vision deep inside her mind.
Ten years later, Lily is introduced to the charismatic Flo and they become best friends. But Lily is guilt-ridden—she is hiding a terrible secret that has the power to destroy both their lives.
When Flo’s father is accused of killing a schoolgirl, the horrors of Lily’s past come bubbling to the surface. Lily knows that, whatever the consequences, she has to make things right. She must go back to the events of her childhood and face what happened at the boat house all those years ago.
Can Lily and Flo discover what is hiding in the murky waters of the lake before the killer strikes again?