When small-town athlete Avery’s morning run leads her to a strange pond in the middle of the forest, she awakens a horror the townspeople of Crook’s Falls have long forgotten. The black water has been waiting. Watching. Hungry for the souls it needs to survive. Avery can smell the water, see it flooding everywhere; she thinks she's losing her mind. And as the black water haunts Avery—taking a new form each time—people in town begin to go missing.

Though Avery had heard whispers of monsters from her Kanien’kéha:ka (Mohawk) relatives, she has never really connected to her Indigenous culture or understood the stories. But the Elders she has distanced herself from now may have the answers she needs. When Key, her best friend and longtime crush, is the next to disappear, Avery is faced with a choice: listen to the Kanien’kéha:ka and save the town but lose her friend forever… or listen to her heart and risk everything to get Key back.